Datasheet ST72T85A5Q6, ST72E85A5G0, ST7285C, ST7285A5CQ8, ST7285A5CQ6 Datasheet (SGS Thomson Microelectronics)

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Page 1

November 1997 1/117

Rev. 1.0

ST7285C

8-BIT MCU FOR RDS WITH 48K ROM, 3K RAM, ADC,

TWO TIMERS, TWO SPIs, I

C AND SCI INTERFACES

■

4.5V to 5.5V Supply Operating Range

■ Operates at 8.664MHz Oscillator Frequency for

RDS compatibility

■

Fully Static operation

■

-40°Cto+85°C Maximum Operating Temperature Range

■

Run, Wait, Slow, Halt and RAM Retention modes

■

User ROM: 48 Kbytes

■ Data RAM: 3 Kbytes, including 128 byte stack

■

80 pin plastic package

■

62 multifunctional bidirectional I/O lines: – Programmable Interrupt inputs on some I/Os – 8 Analog inputs – EMI filtering

■

Two 16-bit Timers, each featuring: – 2 Input Captures – 2 Output Compares – External Clock input (on Timer A) – PWM and Pulse Generator modes

■ RDS Radio Data System Filter, Demodulator

and GBS circuits

■

8-bit Analog-to-Digital converter with 8 channel analog multiplexer

■ Digital Watchdog

■

Two SPI Serial Peripheral Interfaces

■

SCI Serial Communications Interface

■ Full I

C multiple Master/Slave interface

■ 2KHz Beep signal generator

■

Master Reset and Power-On Reset

■

8-bit Data Manipulation

■ 63 Basic Instructions

■

17 main Addressing Modes

■

8 x 8 Unsigned Multiply Instruction

■ True Bit Manipulation

■ Complete Development Support on PC/DOS/

WindowsTMReal-Time Emulator

■

Full Software Package (C-Compiler, CrossAssembler, Debugger)

PQFP80

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Table of Contents

117

ST7285C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

1 GENERAL DESCRIPTION . . . . . . . ...............................................5

1.1 INTRODUCTION .........................................................5

1.2 PIN DESCRIPTION .......................................................6

1.3 MEMORYMAP .........................................................10

2 CENTRAL PROCESSING UNIT .................................................13

2.1 INTRODUCTION ........................................................13

2.2 CPU REGISTERS . . . . . . . . ...............................................13

3 CLOCKS, RESET, INTERRUPTS & POWER SAVING MODES ........................15

3.1 CLOCKSYSTEM........................................................15

3.1.1 General Description .................................................15

3.1.2 Crystal Resonator . . . . . . . . ..........................................15

3.1.3 Ceramic Resonator . . . ..............................................16

3.1.4 External Clock . . . . . . . ..............................................16

3.2 MISCELLANEOUS REGISTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................17

3.3 RESETS...............................................................18

3.3.1 Introduction . . . . . . . . ...............................................18

3.3.2 External Reset . . . . . . . . . . ...........................................18

3.3.3 Reset Operation . . . . . . . . . . . . . . . .....................................18

3.3.4 Power-on Reset . . . . . . . . . . . . . . . .....................................18

3.4 WATCHDOG TIMER SYSTEM (WDG) . . .....................................19

3.4.1 Introduction . . . . . . . . ...............................................19

3.4.2 Functional Description . . . ............................................19

3.4.3 Watchdog Register . . . ..............................................19

3.5 INTERRUPTS . . . . ......................................................20

3.6 POWER SAVING MODES .................................................22

3.6.1 SlowMode........................................................22

3.6.2 WaitMode ........................................................22

3.6.3 HaltMode.........................................................23

4 ON-CHIP PERIPHERALS . . . ...................................................24

4.1 I/OPORTS.............................................................24

4.1.1 Introduction . . . . . . . . ...............................................24

4.1.2 Generic I/O Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................24

4.1.3 I/O Port Implementation . . . . . . . . . . . . ..................................27

4.2 SERIAL COMMUNICATIONS INTERFACE. . ..................................28

4.2.1 Introduction . . . . . . . . ...............................................28

4.2.2 Features . . . . . . . . . . . . . . . ...........................................28

4.2.3 Serial Data Format . .................................................28

4.2.4 Data Reception and Transmission. . . ...................................28

4.2.5 Receiver Muting and Wake-up Feature . . . . ..............................28

4.2.6 Baud Rate Generation . . . ............................................29

4.2.7 SCI Register Overview . . . ............................................29

4.3 16-BIT TIMER . . . . ......................................................35

4.3.1 Introduction . . . . . . . . ...............................................35

4.3.2 Counter . . . . ......................................................35

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Table of Contents

4.3.3 External Clock . . . . . . . ..............................................37

4.3.4 Input Capture . . . ...................................................39

4.3.5 Output Compare . . . . ...............................................40

4.3.6 Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . .........................43

4.4 SERIAL PERIPHERAL INTERFACE . . . . . . . . . . . . . . . . . . . . .....................45

4.4.1 Introduction . . . . . . . . ...............................................45

4.4.2 Features . . . . . . . . . . . . . . . ...........................................45

4.4.3 Functional Description . . . ............................................45

4.4.4 Signal Description . . . . . . . . ..........................................47

4.4.5 Master Out Slave In (MOSI). ..........................................47

4.4.6 Master In Slave Out (MISO) . ..........................................47

4.4.7 Serial Peripheral Control Register (SPCR) ...............................50

4.4.8 Serial Peripheral Status Register (SPSR) . . . . . ...........................51

4.4.9 Serial Peripheral Data I/O Register (SPDR) . . . . . .........................53

4.4.10Single Master And Multimaster Configurations . . . . ........................53

4.5 I2C BUS INTERFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . .........................54

4.5.1 Introduction . . . . . . . . ...............................................54

4.5.2 General Features . . . . ...............................................54

4.5.3 Functional Description . . . ............................................54

4.5.4 EPROM/ROM I C COMPATIBILITY APPLICATION NOTE. . . . ...............56

4.5.5 Re giste r Desc ript ion .................................................57

4.5.6 I2C Stat e Machine: . . . ..............................................61

4.6 A /D CONVERTER (ADC) . .................................................64

4.6.1 Introduction . . . . . . . . ...............................................64

4.6.2 Fu nctio nal De scrip tion . . . ............................................64

4.6.3 Re giste r Desc ript ion .................................................65

4.7 RDS FILTER . . . ........................................................66

4.7.1 Fe atures . . . . . . . . . . . . . . . ...........................................66

4.7.2 Fu nctio nal De scrip tion . . . ............................................67

4.8 RDS DEMODULATOR . . . . . . . . . . . . . . . .....................................68

4.8.1 Fe atures . . . . . . . . . . . . . . . ...........................................68

4.8.2 Fu nctio nal De scrip tion . . . ............................................69

4.9 RDSG.B.S.............................................................72

4.9.1 Introduction . . . . . . . . ...............................................72

4.9.2 Fe atures . . . . . . . . . . . . . . . ...........................................72

4.9.3 Fu nctio nal De scrip tion . . . ............................................74

4.9.4 Ac quisition of Group and Block Synchronization . . . . .......................77

4.9.5 Application Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . .........................77

4.9.6 Block Synchronization Software . . .....................................77

4.9.7 Error Correction s oftwar e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................77

5SOFTWARE ................................................................78

5.1 S T7 ARCHITECTU RE . . . . . . . . . . . . . . . .....................................78

5.2 S T7 ADDRESSING MOD ES ...............................................78

5.3 S T7 INSTRUCT ION SET . .................................................83

6 EL ECT RICAL CHARACTERI STI CS. . . . . . . . . . . . ..................................86

6.1 A BSO LUT E M AXIMUM RATINGS. ..........................................86

6.2 P OWER CONSID ERATIONS . . . . ..........................................87

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Table of Contents

117

6.3 DC ELECTRICAL CHARACTERISTICS ......................................88

6.4 AC ELECTRICAL CHARACTERISTICS ......................................89

6.5 CONTROLTIMING ......................................................89

7 GENERAL INFORMATION . . . . . . . . . . ...........................................96

7.1 PACKAGE MECHANICAL DATA. . . . ........................................96

ST72E85

ST72T85 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97

1 GENERAL DESCRIPTION. . . ...................................................98

1.1 INTRODUCTION ........................................................98

1.2 PIN DESCRIPTION ......................................................99

1.3 MEMORYMAP.........................................................103

1.4 EPROM ERASURE .....................................................105

1.5 EPROM/R OM I C COMPATIBILITY APPLICATION NOTE.......................106

2 ELECTRICAL CHARACTERISTI CS. . . . .........................................107

2.1 ABSOLUTE MAXIMUM RATINGS. . . . . . ....................................107

2.2 POWER CONSIDERATIONS. . . ...........................................108

2.3 DC ELECTRICAL CHARACTERISTICS .....................................109

2.4 AC ELECTRICAL CHARACTERIS TICS. . . ...................................110

2.5 CONTROLTIMING......................................................110

3 GENERAL INFORMATION . . . . . . . . . . ..........................................117

3.1 PACKAGE MECHANICAL DATA. . . . .......................................117

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ST7285C

1 GENERAL DESCRIPTION

1.1 INTRODUCTION

The ST7285C HCMOS Microcontroller Unit is a member of the ST7 family of Microcontrollers dedicated to car radio applications with RDS capability. The device is based on an industry-standard 8bit core and features an enhanced instruction set. The device is normally operated at an 8.664MHz oscillator frequency for RDS compatibility but, thanks to the fully static design, operation is possible down to DC, when RDS functionality is not required. Under software control, theST7285C may be placed in either WAIT, SLOW or HALT modes, thus reducing power consumption. The enhanced instruction set and addressing modes afford real programming potential. In addition to standard 8bit data management, theST7285C features true bit manipulation, 8x8 unsigned multiplication and indirect addressing modes.

The device includes an on-chip oscillator, CPU, ROM, RAM, 62 I/O lines and the following on-chip peripherals: Analog-to-Digital converter (ADC), two industry standard SPI serial interfaces, a Serial Communications Interface, an I2C interface, a digital Watchdog Timer, two independent 16-bit Timers, one featuring an External Clock Input, and both featuring Pulse Generator capabilities, 2 Input Captures and 2 Output Compares. RDS Filter, Demodulator and GBS circuitry for car radio applications is also included.

NOTE

FOR THIS DEVICE, SGS-THOMSON CAN ONLY RECEIVE MOTOROLA S19 FORMAT FOR ROM CODES.

Figure 1. ST7285C Block Diagram

*On EPROM or OTP versions only.

Power on Reset

PA0 - PA7

Pin 65..72

PB0 - PB7

Pin 73..80

OSCin

OSCout

RESET

/ TEST

OSC

8 -BIT CORE

ALU

VR01735P

Internal CLOCK

ADDRESSand DATA BUS

TimerA

PORT A

PORT B

A/D Converter

SPI B

PORT C

PC0 - PC7

Pin 5..12

SPI A

PORT D

SCI

RAM

RDS

FILTER,DEMOD,GBS

TimerB

PD0 - PD7

Pin 13..20

PORT E

PE0 - PE7

Pin 25..32

PORT F

PF0 - PF7 Pin 33..40

PORT H

PORT G

PH0 - PH5

Pin 53..58

PG0 - PG7

Pin 45..52

ROMor EPROM*

48k

Watchdog

RDScomp

MPX

RDS fil RDS ref

ARS AINT

DDPVSSPVDDAVSSA

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ST7285C

1.2 PIN DESCRIPTION

All I/Os from Port A to Port D, as well as PH0, 1 and 2, feature alternate function compatibility. Software selectable input pull-ups are available on

ports featuring interrupt capability (PC4, PC5, PD4, PD5, PF0-PF3, PG3).

VSSA VDDA MPX RDSREF RDSFIL RDSCOMP PH5 PH4 PH3 PH2/RDSDATA PH1/RDSCLKOUT PH0/RDSQUAL PG7 PG6 PG5 PG4 PG3 PG2 PG1 PG0 ARS AINT VDDP VSSP

VSSP VDDP OSCOUT OSCIN PC0/MISO_B PC1/MOSI_B PC2/SCK_B PC3/SS_B PC4/OC2_B PC5/OC1_B PC6/IC2_B PC7/IC1_B PD0/MISO_A PD1/MOSI_A PD2/SCK_A PD3/SS_A PD4 PD5 PD6/SCL PD7/SDA RESET VPP*/TEST VDD VSS

1 2 3 4 5 6 7 8 9 (I10) 10 (I10) 11 12 13 14 15 16 17 (I9) 18 (I9) 19 20 21 22 23 24

64 63

62 61 60 59 58 57 56 55 54 53 52 51 50 49

(I1) 48

47 46 45 44 43 42

80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65

25 26 27 28 29 30 31 32 37 38 39

PB7/BEEP/

CLKOUT

PB6/CLKEXT

PB5/OC2_A

PB4/OC1_A

PB3/IC2_A

PB2/IC1_A

PB1/RDI

PB0/TDO

PA7/AIN7

PA6/AIN6

PA5/AIN5

PA4/AIN4

PA3/AIN3

PA2/AIN2

PA1/AIN1

PA0/AIN0

PE0

PE1

PE2

PE3

PE4

PE5

PE6

PE7

PF0

PF1

PF2

PF3

PF4

PF5

PF6

PF7

33 34 35 36

*) On EPROM/OTPversions only

(I2)(I2)(I2)(I2)

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ST7285C

Pin Pin Name(s) Basic Function Alternate Function Remarks

SSP

Ground for Output Buffers

This pin is connected to pin 41

DDP

Power Supply for Output Buffers

This pin is connected to pin 42

3 OSCOUT Oscillator Output pin. 4 OSCIN Oscillator Input pin.

5 PC0/MISO_B I/O Port PC0

SPI B master in/slave out data input/output

Alternate function or I/O. The I/O configuration is software selectable as triggered input or push pull output.

6 PC1/MOSI_B I/O Port PC1

SPI B Master Out/ Slave In Data Input/

Output 7 PC2/SCK_B I/O Port PC2 SPI B Serial Clock 8 PC3/SS_B I/O Port PC3 SPI B Slave Select

9 PC4/OC2_B I/O Port PC4

Output Compare 2

on Timer B

Alternate function or I/O. Software selectable as triggered input, push pull output, or triggered interrupt input with pull up (Interrupt I10).

10 PC5/OC1_B I/O Port PC5

Output Compare 1

on Timer B

11 PC6/IC2_B I/O Port PC6

Input Capture 2

on Timer B

Alternate function or I/O. The I/O configuration is software selectable as triggered input or push pull output.

12 PC7/IC1_B I/O Port PC7

Input Capture 1

on Timer B.

13 PD0/MISO_A I/O Port PD0

SPI A Master In/Slave

Out Data Input/Output

14 PD1/MOSI_A I/O Port PD1

SPI A Master Out/

Slave In data Input/

Output

15 PD2/SCK_A I/O Port PD2 SPI A Serial Clock 16 PD3/SS_A I/O Port PD3 SPI A Slave Select 17 PD4 I/O Port PD4 - Software selectable as triggered input, push

pull output, open drain output or triggered interrupt input with pull up (Interrupt I9).

18 PD5 I/O Port PD5 19 PD6/SCL I/O Port PD6 I

C Serial Clock Alternate function or I/O. The I/O configuration

is software selectable as triggered input or open drain output.

20 PD7/SDA I/O Port PD7 I

C Serial Data

21 RESET General Reset -

Bidirectional. An active low signal forces MCU initialization. This event is the top priority nonmaskable interrupt. As an output, it can be used to reset external peripherals.

22 TEST RESERVED -

Input. This pin MUST be tied directly to V

during normal operation.

23 V

Power Supply forall logic circuitry

Except for output buffers and pull-ups.

24 V

Ground for all logic circuitry

25 PE0 I/O Port PE0 -

Software selectable as triggered input or push pull output.

26 PE1 I/O Port PE1 27 PE2 I/O Port PE2 28 PE3 I/O Port PE3 29 PE4 I/O Port PE4 30 PE5 I/O Port PE5 31 PE6 I/O Port PE6 32 PE7 I/O Port PE7 -

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ST7285C

33 PF0 I/O Port PF0 -

Software selectable as triggered input, a push pull output, open drain output, or triggered interrupt input with pull up (Interrupt I2).

34 PF1 I/O Port PF1 35 PF2 I/O Port PF2 36 PF3 I/O Port PF3 37 PF4 I/O Port PF4 -

Software selectable as a triggered input or as a push pull output.

38 PF5 I/O Port PF5 39 PF6 I/O Port PF6 40 PF7 I/O Port PF7 -

41 V

SSP

Ground for Output Buffers.

- This pin is connected to pin 1.

42 V

DDP

Power Supply for Output Buffers

- This pin is connected to pin 2.

43 AINT Reserved - Must be tied to 5V 44 ARS Reserved - Must be tied to 5V 45 PG0 I/O Port PG0 -

Software selectable as triggered input or push pull output.

46 PG1 I/O Port PG1 47 PG2 I/O Port PG2 -

48 PG3 I/O Port PG3 -

Software selectable as triggered input, a push pull output, open drain output, or triggered interrupt input with pull up (Interrupt I1).

49 PG4 I/O Port PG4 -

Software selectable as triggered input or push pull output. Note that PH0, 1, 2 offer alternate function capabilities for test purposes.

50 PG5 I/O Port PG5 51 PG6 I/O Port PG6 52 PG7 I/O Port PG7 -

PH0/ RDSQUAL

I/O Port PH0 RDS Quality signal

PH1/ RDSCLKOUT

I/O Port PH1

RDS GBS Clock Out signal

PH2/

RDSDATA

I/O Port PH2 RDS GBS Data signal

56 PH3 I/O Port PH3 -

Software selectable as triggered input or high voltage (10V max) open drain output.

57 PH4 I/O Port PH4 58 PH5 I/O Port PH5 -

59 RDSCOMP RDS Comp Input signal

Used to feed theDemodulator froman external filter when the internal filter is switched off.

60 RDSFIL

RDS Filtered Output signal

Used for Demodulator test purposes.

61 RDSREF RDS Input Reference 62 MPX RDS input signal 63 V

DDA

Analog Power Supply

For RDS and ADC circuits

64 V

SSA

Analog Ground

65 PA0/AIN0 I/O Port PA0

Analog input to ADC

Alternate function or I/O. The I/O configuration is software selectable as triggered input or push pull output. Note that when a pin is used as Analog input it must not be configured as an output to avoid conflicts with the analog voltage to be measured.

66 PA1/AIN1 I/O Port PA1 67 PA2/AIN2 I/O Port PA2 68 PA3/AIN3 I/O Port PA3 69 PA4/AIN4 I/O Port PA4 70 PA5/AIN5 I/O Port PA5 71 PA6/AIN6 I/O Port PA6 72 PA7/AIN7 I/O Port PA7

Pin Pin Name(s) Basic Function Alternate Function Remarks

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ST7285C

73 PB0/TDO I/O Port PB0

SCI Transmit Data Out

Alternate function or I/O. The I/O configuration is software selectable as triggered input or push pull output.

74 PB1/RDI I/O Port PB1 SCI Receive Data In 75 PB2/IC1_A I/O Port PB2

Input capture 1 on Timer A

76 PB3/IC2_A I/O Port PB3

Input capture 2 on Timer A

77 PB4/OC1_A I/O Port PB4

Output compare 1 on Timer A

78 PB5/OC2_A I/O Port PB5

Output compare 2 on Timer A

79 PB6/CLKEXT I/O Port PB6

External Clock on Timer A

PB7/BEEP/ CLKOUT

I/O Port PB7 BEEP or CPU Clock.

This pin can be a push pull output delivering the Beep signal (2KHz) or the CPU clock, according to the miscellaneous register settings.

Pin Pin Name(s) Basic Function Alternate Function Remarks

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ST7285C

1.3 MEMORY MAP Table 1. Memory Map

Address Block Register name

Reset

Status

Remarks

0000h 0001h 0002h 0003h

Port A

Data Reg Data Direction Reg Not Used Not Used

00h 00h

R/W Register R/W Register Absent

Absent 0004h 0005h

0006h 0007h

Port B

Data Reg Data Direction Reg Not Used Not Used

00h 00h

R/W Register

Absent

Absent 0008h

0009h 000Ah 000Bh

Port C

Data Reg Data Direction Reg Option Reg Not Used

00h 00h

--00----b

R/W Register

Absent 000Ch

000Dh 000Eh 000Fh

Port D

Data Reg Data Direction Reg Option Reg Not Used

00h 00h

--00----b

R/W Register

Absent 0010h

0011h 0012h 0013h

Port E

Data Reg Data Direction Reg Not Used Not Used

00h 00h

R/W Register

Absent

Absent 0014h

0015h 0016h 0017h

Port F

Data Reg Data Direction Reg Option Reg Not Used

00h 00h

----0000b

R/W Register

Absent 0018h

0019h 001Ah 001Bh

Port G

Data Reg Data Direction Reg Option Reg Not Used

00h 00h

----0---b

R/W Register

Absent 001Ch

001Dh 001Eh 001Fh

Port H

Data Reg Data Direction Reg Not Used Not Used

00h 00h

R/W Register

Absent

Absent 0020h

Miscellaneous Reg-

ister

00h see register description

0021h 0022h 0023h

SPI A

Data I/O Reg Control Reg Status Reg

XXh

0xh 00h

R/W Register

Read Only Register 0024h WDG Watchdog register 7Fh see register description 0025h

0026h 0027h

SPI B

Data I/O Reg Control Reg Status Reg

XXh

0xh 00h

R/W Register

Read Only Register

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ST7285C

0028h 0029h 002Ah 002Bh 002Ch 002Dh 002Eh

CR: Control Register SR1: Status Register 1 SR2: Status Register 2 CCR: Clock Control Register OAR1: Own Address Register 1 OAR2: Own Address Register 2 DR: Data Register

00h 00h 00h 00h 00h 00h 00h

R/W Register

Read Only Register

R/W Register

R/W Register 002Fh 0030h

RESERVED

0031h 0032h 0033h 0034h 0035h 0036h 0037h 0038h 0039h 003Ah 003Bh 003Ch 003Dh 003Eh 003Fh

Timer A

Control Reg2 Control Reg1 Status Reg Input Capture1 High Register Input Capture1 Low Register Output Compare1 High Register Output Compare1 Low Register Counter High Register Counter Low Register Alternate Counter High Register Alternate Counter Low RegisteR Input Capture2 High Register Input Capture2 Low Register Output Compare2 High Register Output Compare2 Low Register

00h

00h XXh XXh XXh XXh XXh FFh FCh

00h

00h XXh XXh XXh XXh

R/W Register R/W Register Read Only Register Read Only Register Read Only Register R/W Register R/W Register Read Only Register Read Only Register Read Only Register Read Only Register Read Only Register Read Only Register R/W Register

R/W Register 0040h RESERVED 0041h

0042h 0043h 0044h 0045h 0046h 0047h 0048h 0049h 004Ah 004Bh 004Ch 004Dh 004Eh 004Fh

Timer B

Control Reg2 Control Reg1 Status Reg Input Capture1 High Register Input Capture1 Low Register Output Compare1 High Register Output Compare1 Low Register Counter High Register Counter Low Register Alternate Counter High Register Alternate Counter Low Register Input Capture2 High Register Input Capture2 Low Register Output Compare2 High Register Output Compare2 Low Register

00h

00h XXh XXh XXh XXh XXh FFh FCh

00h

00h XXh XXh XXh XXh

0050h 0051h 0052h 0053h 0054h 0055h 0056h 0057h

SCI

SCI Prescaler

SCSR: Status Register SCDR: Data Register SCBRR: Baud Rate Register SCCR1: Control Register 1 SCCR2: Control Register 2 PSCBRR: Receive Baud Rate Reg Reserved PSCBRT: Transmit Baud Rate Reg

1100000xb

XXh

00x----xb

XXh

00h

---

00h

Read Only Register R/W Register R/W Register R/W Register R/W Register R/W Register Reserved ST use

R/W Register 0058h RESERVED 0059h RESERVED 005Ah

005Bh

RDS Filter

RDS FI1 RDS FI2

R/W Register

Address Block Register name

Reset

Status

Remarks

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ST7285C

005Ch 005Dh 005Eh 005Fh

RDS Demodulator

RDS DE1 RDS DE2 RDS DE3 RDS DE4

see register description

0060h 0061h 0062h 0063h 0064h 0065h 0066h 0067h 0068h 0069h 006Ah 006Bh 006Ch 006Dh 006Eh 006Fh

RDS GBS

SR0 -Shift Reg 0 SR1 -Shift Reg 1 SR2 -Shift Reg 2 SR3 -Shift Reg 3 SY0 -Polynomial Reg 0 SY1 -Polynomial Reg 1 GS_CNT Count Reg GS_INT Interrupt Reg DR0 -RDSDAT Reg 0 DR1 -RDSDAT Reg 1 DR2 -RDSDAT Reg 2 DR3 -RDSDAT Reg 3 QR0 -QUALITY Reg 0 QR1 -QUALITY Reg 1 QR2 -QUALITY Reg 2 QR3 -QUALITY Reg 3

see register description

0070h 0071h

ADC

Data Reg Control/Status Reg

XXh

00h

Read Only Register

R/W Register

0072h to

007Fh

RESERVED

0080h to

0BFFh

0C00h to

0C7Fh

RAM 3K Bytes

of which

STACK 128 Bytes

User variables and subroutine nesting

0C80h to

3FFFh

RESERVED

4000h to

FFDFh

ROM 48K bytes

(49120 bytes)

User application code and data

FFE0h to

FFFFh

User vectors Interrupt and Reset Vectors

Address Block Register name

Reset

Status

Remarks

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ST7285C

2 CENTRAL PROCESSING UNIT

2.1 INTRODUCTION

The CPU has a full 8-bit architecture. Six internal registers allow efficient 8-bit data manipulation. The CPU is capable of executing 63 basic instructions and features 17 main addressing modes.

2.2 CPU REGISTERS

The 6 CPU registers are shown in the programming model inFigure 2. Following an interrupt, all registers except Y are pushed onto the stack in the order shown in Figure 3. They are popped from stack in the reverse order.

Accumulator (A). The Accumulator is an 8-bit general purpose register used to hold operands

and the results of the arithmetic and logic calculations as well as data manipulations.

Index Registers (X and Y).These 8-bit registers are used to create effective addresses or as temporary storage areas for data manipulation. The Cross-Assembler generates a PRECEDE instruction (PRE) to indicate that the following instruction refers to the Y register. The Y register is never automatically stacked. Interrupt routines must push or pop it by using the PUSH and POP instructions.

Program Counter (PC).The program counter is a 16-bit register containing the address of the next instruction to be executed by the CPU.

Figure 2. Organization of Internal CPU Registers

ACCUMULATOR:

X INDEX REGISTER:

Y INDEX REGISTER:

PROGRAM COUNTER:

STACKPOINTER:

CONDITION CODE REGISTER:

X = Undefined

RESET VALUE:

XXXXXXXX

RESET VALUE:

XXXXXXXX

RESET VALUE:

XXXXXXXX

RESET VALUE = DEVICE DEPENDENT,SEE MEMORY MAP

RESET VALUE:

XXXXXXXX

RESET VALUE = DEVICE DEPENDENT,SEE MEMORY MAP

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ST7285C

CPU REGISTERS(Cont’d) Stack Pointer (SP) The Stack Pointer is a 16-bit

register. Since the stack size can vary from device to device, the appropriate number of most significant bits are forced so as to map the stack as defined in the Memory Map. The number of least significant digits thus available tothe user will depend on the stack size, for example in the case of a 128 byte stack, 7 bits will be available whereas in the case of a64 byte stack, only 6 bits will beavailable.

The stack is used to save the CPU context during subroutine calls or interrupts. The user may also directly manipulate the stack by means of the PUSH and POP instructions.

Following an MCU Reset, or after a Restore following a Reset Stack Pointer instruction (RSP), the StackPointer is set to point to thehighest location in the stack. It is then decremented after data has been pushed onto the stack and incremented after data is popped from the stack. When the lower limit is exceeded, the Stack Pointer wraps around to the stack upper limit. The previously stored information is then overwritten and therefore lost. The upper and lower limits of the stack area are shown in the Memory Map.

A subroutine call occupies two locations and an interrupt five locations in the stack area.

Condition Code Register (CC) The Condition Code register is a 5-bit register which indicates the result of the instruction just executed as wellas the

state of the processor. These bits can be individually tested by a program and specified action taken as a result of their state. The following paragraphs describe each bit of the CC register in turn.

Half carry bit (H)The H bit is set to 1 when acarry occurs between bits 3 and 4 of the ALU during an ADD or ADC instruction. The H bit is useful in BCD arithmetic subroutines.

Interrupt mask (I) When the I bit is set to 1, all interrupts except the TRAP software interrupt are disabled. Clearing this bit enables interrupts to be passed to the processor core. Interrupts requested while I is set are latched and can be processed when I is cleared (only one interrupt request per interrupt enable flag can be latched).

Negative (N)

When set to 1, this bit indicates that the result of the last arithmetic, logical or data manipulation is negative (i.e. the most significant bit is a logic 1).

Zero (Z)

When set to 1, this bit indicates that the result of the last arithmetic, logical or data manipulation is zero.

Carry/Borrow (C) When set, C indicates that a carry or borrow out of the ALU occured during the last arithmetic operation. This bit is also affected during execution of bit test, branch, shift, rotate and store instructions.

Figure 3. Stacking Order

INCREASING

MEMORY

UNSTACK

ACCUMULATOR

X INDEX REGISTER

PCH PCL

(PUSH)

DECREASING

MEMORY

111

VR000074

ADDRESSES

STACK

(POP)

CONDITION CODE

RETURN

INTERRUPT

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ST7285C

3 CLOCKS, RESET, INTERRUPTS & POWER SAVING MODES

3.1 CLOCK SYSTEM

3.1.1 General Description

The MCU accepts either a Crystal or Ceramic resonator, or an external clock signal to drive the internal oscillator. The internal clock (CPU CLK running at f

CPU

) is derived from the external oscillator

frequency (f

OSC).

The external Oscillator clock is first divided by 2, and an additional division factor of 2, 4, 8, or 16 can be applied, in Slow Mode, to reduce the frequency of the CPU clock (see note 1); this clock signal is also routed to the onchip peripherals. The CPU clock signal consists of a square wave with a duty cycle of 50%.

Figure 4. External Clock Source Connections

Figure 5. Equivalent Crystal Circuit

3.1.2 Crystal Resonator

The internal oscillator is designed to operate with an AT-cut parallel resonant quartz crystal resonator in the frequency range specified for f

osc

.The circuit shown in Figure 6 is recommended when using a crystal, andTable 2 lists the recommended capacitance and feedback resistance values. The crystal and associated components should be mounted as close as possible to the input pins in order to minimize output distortion and start-up stabilisation time.

Use of an external CMOS oscillator is recommended when crystals outside the specified frequency ranges are to be used.

Figure 6. Crystal/Ceramic Resonator

Figure 7. Clock Prescaler Block Diagram

Note 1: Additional division factor of CPU clock is only available on L5/L6.

OSC

out

EXTERNAL

CLOCK

OSC

out

OSC

out

OSCin

OSCout

OSC

out

OSCin

OSCout

%2 %2,4,8,16

CPUCLK to CPU and Peripherals

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ST7285C

CLOCK SYSTEM (Cont’d)

3.1.3 Ceramic Resonator

A ceramic resonator may be used as an alternative to a crystal in low-cost applications. The circuit shown in Figure 6 is recommended when using a ceramic resonator. Table 3 lists the recommended feedback capacitance and resistance values. The manufacturer of the particular ceramic resonator being considered should be consulted for specific information.

Table 2. Recommended Values for Crystal

Resonator

3.1.4 External Clock

An external clock may be applied to the OSCin input with the OSCout pin not connected, as shown on Figure 4. The t

OXOV

and t

ILCH

specifications do not apply when using an external clock input. The equivalent specification of the external clock source should be used instead of t

OXOV

or t

ILCH

See CONTROL TIMING SECTION.

Table 3.Recommended Values for Ceramic

Resonator

Figure 8. Timing Diagram for Internal CPU Clock Frequency transistions

2MHz 4MHz 8MHz Unit

SMAX

400 75 60 Ω

5 7 10 pF

81215fF

OSCin

15-40 15-30 15-25 pF

OSCout

15-30 15-25 15-20 pF

10 10 10 MΩ

Q304060

2-8MHz Unit

SMAX

10 Ω

40 pF

4.3 pF

OSCin

30 pF

OSCout

30 pF

1-10 MΩ

Q 1250

MISCELLANEOUS REGISTER

00 10

VR02062B

New frequency requested

New frequency active when

OSC

/4 & f

OSC

/8 = 0

Normalmode

active

Normalmode requested

PSM1:PSM0

SMS

OSC

CPU

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ST7285C

3.2 MISCELLANEOUS REGISTER

The Miscellaneous register allows one to select the SLOW operating mode and to set the clock division prescaler factor. Bits 3 and 4 allow one to set PB7 functionality (I/O, CPU Clock o/p or Beep signal o/p), while bits 6 and 7 determine the signal conditions which will trigger an interrupt request on I/O pins having interrupt capability.

b7, b6 -

EI1, EI0

External Interrupt Option

0 0 - Negative edge and low level (Reset state) 1 0 - Negative edge only 0 1 - Positive edge only 1 1 - Positive and negative edge

This selection applies globally to the four external interrupts: I1, I2, I9 and I10.

b6 and b7 can be written only when the Interrupt Mask (I) of the CC (Condition Code) register is set to 1.

b5- Reserved b4, b3 - SK1, CK0

Clock/Beep Output

0 0 - I/O port (Reset state) 1 0 - I/O port 0 1 - CPU Clock output to pin PB7 1 1 - 2KHz Beep signal output to pin PB7 (at 8.664 MHz oscillator frequency)

b2, b1 - SM1,SM0:

CPU clock prescaler for Slow

Mode

0 0 - Oscillator frequency / 4 1 0 - Oscillator frequency / 8 0 1 - Oscillator frequency / 16 1 1 - Oscillator frequency / 32

b0 - SMS:

Slow Mode Select

0- Normal mode - Oscillator frequency / 2

(Reset state)

1- Slow mode (Bits b1 and b2 define the prescaler

factor)

EI1 EI0 b5 SK1 CK0 SM1 SM0 SMS

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3.3 RESETS

3.3.1 Introduction

There are four sources of Reset: – RESET pin (external source) – Power-On Reset (Internal source) – WATCHDOG (Internal Source) The Reset Service Routine vector is located at ad-

dress FFFEh-FFFFh.

3.3.2 External Reset

The RESET pin is both an input and an open-drain output with integrated pull up resistor. When one of the internal Reset sources is active, the Reset pin is driven low to reset the whole application.

3.3.3 Reset Operation

The duration of the Reset condition, which is also reflected on the output pin, is fixed at4096 internal CPU Clock cycles. A Reset signal originating from an external source must have a duration of at least

1.5 internal CPU Clock cycles in order to be recognised. At the end of the Power-On Reset cycle, the MCU may be held in the Reset condition by an External Reset signal. The RESET pin may thus be used to ensure VDDhas risen to a point where the MCU can operate correctly before the User program is run. Following a Reset event, or after exit-

ing Halt mode, a 4096 CPU Clock cycle delay period is initiated in order to allow the oscillator to stabilise and to ensure that recovery has taken place from the Reset state.

During the Reset cycle, the device Reset pin acts as an output that is pulsed low for 3 machine cycles (6 oscillator cycles). In its high state, an internal pull-up resistor of about 300KΩ is connected to the Reset pin. This resistor can be pulled low by external circuitry to reset the device.

3.3.4 Power-on Reset

This circuit detects the ramping up of VDD,and generates a pulse thatis used to reset the application (at approximately VDD= 2V).

Power-On Reset is designed exclusively to cope with power-up conditions, and should not be used in order to attempt to detect a drop in the power supply voltage.

Caution:

to re-initialize the Power-On Reset, the power supply must fall below approximately 0.8V (Vtn), prior to rising above 2V. If this condition is not respected, on subsequent power-up the Reset pulse may not be generated. An external pulse may be required to correctly reactivate the circuit.

Figure 9. Reset Block Diagram

VDD

COUNTER

RESET

to ST7

VR2062C

300K

WATCHDOG RESET

OR DLPSS

RESET

OSCILLATOR

SIGNAL

INTERNAL

RESET

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ST7285C

3.4 WATCHDOG TIMER SYSTEM (WDG)

3.4.1 Introduction

The Watchdog timer is used to detect the occurence of a software fault, usually generated by external interference or by unforeseen logical conditions, which causes the application program to abandon its normal sequence. The Watchdog circuit generates an MCU reset on expiry of a programmed time period, unless the program refreshes the counter’s contents before it is decremented to zero.

3.4.2 Functional Description

The counter is decremented every 12,288 machine cycles, and the length of the timeout period can be programmed by the user in 64 increments, ranging from 12,288 machine cycles to 786,432 machine cycles, depending on the value loaded in bits 0-5 of the Watchdog register. The application program must be written so that the Watchdog register is reloaded at regular intervals during normal operation.

The Watchdog is not activated automatically on Reset, and must be activated by the user program if required. Once activated it cannot be disabled, save by a Reset.

This resistor can be pulled low by external circuitry to reset the device.

The Watchdog delay time is defined by bits 5-0 of the Watchdog register; bit 6 must always be set in order to avoid generating an immediate reset.

Conversely, this can be used to generate a software reset (bit 7 = 1, bit 6 = 0).

Once bit 7 is set, it cannot be cleared by software: i.e. the Watchdog cannot be disabled by software without generating a Reset. The Watchdog timer mustbe reloaded before bit 6 is decremented to ”0” to avoid a Reset. Following a Reset, the Watchdog register will contain 7Fh (bits 0-6 = 1, bit 7 = 0).

If the Watchdog is activated, the HALT instruction will generate a Reset.

If the circuit is not used as a Watchdog (i.e. bit 7 is never set), bits 6 to 0 may be used as a simple 7bit timer, for instance as a real time clock. Since no interrupt will be generated under these conditions, the Watchdog register must be monitored by software.

3.4.3 Watchdog Register

b7 = WDGA: Activation bit (is active if set) b6-0 =

T6-T0

: 7-bit timer counter (Msb to Lsb)

Table 4. Watchdog Timing (f

OSC

= 8 MHz)

WDGA T6 T5 T4 T3 T2 T1 T0

WDG Register initial

value

WDG timeout period (ms)

FF 197 C0 3

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ST7285C

3.5 INTERRUPTS

A list of interrupt sources is given inTable 5below, together with relevant details for each source. Interrupts are serviced according to their order ofpriority, starting with I0, which has the highest priority, and so to I11, which has the lowest priority.

The following list describes the origins for each interrupt level:

– I0 connected to Software Interrupt (TRAP) – I1 connected to Port G3 – I2 connected to Port F0, F1, F2, F3 – I3 connected to SPI A – I4 connected to Timer A – I5 connected to GBS interrupt

– I6 connected to Timer B – I7 connected to SPI B – I8 connected to SCI – I9 connected to Ports D4, D5 – I10 connected to Ports C4, C5 – I11 connected to I2C Exit from HALT mode may only be triggered by an External Interrupt on one of the following ports: C4(I10), C5(I10), D4(I9), D5(I9), F0(I2), F1(I2), F2(I2), F3(I2) and G3(I1).

If more than one input pin of a group connected to the same interrupt line is selected simultaneously, these will be logically ORed.

Table 5. Interrupt Mapping

Interrupt

source

Vector

Address

Interrupts Register

Flag

name

CPU

interrupts

- FFFEh-FFFFh Reset N/A N/A RESET I0 FFFCh-FFFDh Software N/A N/A TRAP I1 FFFAh-FFFBh Ext. Interrupt (Port G3) N/A N/A INT1 I2 FFF8h-FFF9h Ex. Interrupt (Ports F0, F1, F2, F3) N/A N/A INT2 I3 FFF6h-FFF7h Transfer Complete SPI A Status SPIF1_A SPI_A

“ “ Mode Fault “ MODF1_A “

I4 FFF4h-FFF5h Input Capture 1 Timer A Status ICF1_A TIMER_A

“ “ Output Compare 1 “ OCF1_A “ “ “ Input Capture 2 “ ICF2_A “ “ “ Output Compare 2 “ OCF2_A “ “ “ Timer Overflow “ TOF_A “

I5 FFF2h-FFF3h RDS Block Interrupt. RDS GRP

VSI CNI

GBS

I6 FFF0h-FFF1h Input Capture 1 Timer B Status ICF1_B TIMER_B

“ “ Output Compare 1 “ OCF1_B “ “ “ Input Capture 2 “ ICF2_B “ “ “ Output Compare 2 “ OCF2_B “ “ “ Timer Overflow “ TOF_B “

I7 FFEEh-FFEFh Transfer Complete SPI B Status SPIF2_B SPI_B

“ “ Mode Fault “ MODF1_B “

I8 FFECh-FFEDh Transmit Buffer Empty SCI Status TDRE SCI

“ “ Transmit Complete “ TC “ “ “ Receive Buffer Full “ RDRF “ “ “ Idle Line Detect “ IDLE “ “ “ Overrun “ OR “

I9 FFEAh-FFEBh Ext. Interrupt (Ports D4,D5) N/A N/A INT9

I10 FFE8h-FFE9h Ext. Interrupt (Port C4, C5) N/A N/A INT10 I11 FFE6h-FFE7h Byte Transmission Finished I

C Status BTF I2C “ “ Bus Error “ BERR I2C “ “ Stop Detection “ SSTOP I2C

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ST7285C

INTERRUPTS (Cont’d) Figure 10. Interrupt Processing Flowchart

Note 1. See Table 5 . Interrupt Mapping

FROM RESET

TRAP

FETCH NEXT

INSTRUCTION

OF APPROPRIATE INTERRUPT

SERVICEROUTINE

EXECUTE INSTRUCTION

PUSH

PC,X,A,CC

SET I BIT TO 1

VR01172B

LOAD PC

WITH APPROPRIATE

INTERRUPT VECTOR

(1)

I BIT = 1

ONTO STACK

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ST7285C

3.6 POWER SAVING MODES

3.6.1 Slow Mode

The following Power Saving mode may be selected by setting the relevant bits in the Miscellaneous register as detailed in Section3.2.

In Slow Mode, the oscillator frequency can be divided by 4, 8, 16 or 32 rather than by 2. The CPU and peripherals are clocked at this lower frequency, and therefore the RDS filter cannot operate correctly in this mode. SLOW mode is used to reduce power consumption, and enables the user to adapt clock frequency to available supply voltage.

3.6.2 Wait Mode

WAIT mode places the MCU in a low power consumption mode by stopping the CPU. All peripherals remain active. During WAIT mode, the I bit (CC Register) is cleared, so as to enable all interrupts. All other registers and memory remain unchanged. The MCU will remain in WAIT mode until an Interrupt or Reset occurs, whereupon the Program Counter branches to the starting address of the Interrupt or Reset Service Routine.

Refer to Figure 11 below.

Figure 11. Wait Mode Flow Chart

WAIT

VR02062D

EXTERNAL

INTERRUPT

RESET

RESTART

PROCESSORCLOCK

FETCHRESET

VECTOROR

SERVICEINTERRUPT

PERIPHERAL

INTERRUPT

ACTIVE OSCILLATOR

AND PERIPHERALS

CLOCKSACTIVE

PROCESSORCLOCK

STOPPED

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ST7285C

POWER SAVING MODES(Cont’d)

3.6.3 Halt Mode

The HALT instruction places the MCU in its lowest power consumption mode. In HALT mode the internal oscillator is turned off, causing all internal processing to be halted. During HALT mode, the I bit in the CC Register is cleared so as to enable External Interrupts.

All other registers and memory remain unaltered and all Input/Output lines remain unchanged. This

state will endure until an External Interrupt (I1, I2, I9, I10) or a Reset is generated, whereupon the internal oscillator is restarted. A delay of 4096 CPU clock cycles is initiated prior to restarting the application, in order to allow the oscillator to stabilize.

The External Interrupt or Reset causes the Program Counter to be set to the address of the corresponding Interrupt or Reset Service Routine.

Figure 12. Halt Mode Flow Chart

VR02062E

EXTERNAL

INTERRUPT

WAIT

HALT

STOP OSCILLATOR

ANDALL CLOCKS

CLEARI-BIT

RESET

OSCILLATOR

IN SLOW MODE

TURN ON

OSCILLATOR

WAIT FOR 4096 CPU CLOCK TIME DELAY

FETCH RESET

VECTOROR

SERVICEINTERRUPT

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ST7285C

4 ON-CHIP PERIPHERALS

4.1 I/O PORTS

4.1.1 Introduction

Each I/O Port can contain up to 8 individually programmable I/Os. The MCU features seven 8-bit Ports (A, B, C,... G) and one 6-bit-port (H). Each I/ O pin is dedicated to its main functionality, thus reducing and simplifying its programmability.

The current chapter describes the generic I/O structure used in the MCU.

All I/Os are based on a generic circuit, of which a block diagram is given inFigure 13. In most cases the functions are simplified, and several subblocks may be missing (such as, for instance, the analog switch on ports B to H or pull-up and interrupt logic for most of the I/O ports). Some registers may also be absent where their functionality is redundant: it is therefore advisable to consult the Memory Map in section1.3 and the pin description in section 1.2 for proper use of any particular I/O.

Only ports C4, C5, D4, D5, F0,F1, F2, F3, G3 feature interrupt capability.

The following sub-section 4.1.2 contains generic information on ST7 I/O ports. For information specific to this device, please refer to sub-section

4.1.3.

4.1.2 Generic I/O Features

The I/O ports offer the following generic features: – inputs with Schmitt trigger – analog inputs, when connected via internal mul-

tiplexer – interrupt generation, maskable by software – EMI compliance thanks to reduced noise radia-

tion due to lowered cross-current in push pull

mode and reduced input susceptibility. This fea-

ture is particularly relevant in RDS applications. Each

generic

I/O pin may be individually program-

mable by software as: – input: no pull-up, no interrupt generation – input: pull-up, no interrupt generation

– input: pull-up, interrupt generation – input: pull-down, no interrupt generation – output: push-pull – output: open-drain, no pull-up – output: open-drain, with pull-up

4.1.2.1 Port Registers

Each port may be associated with up to four registers:

–

DATA REGISTER

(DR)

Address 0000 0000 000x xx00b; always present.

–

DATA DIRECTION REGISTER

(DDR)

Address 0000 0000 000x xx01b; always present.

–

OPTION REGISTER

(OR) Address 0000 0000 000x xx10b; depending on I/O dedication.

– PULL-UP REGISTER(PUR)

Address 0000 0000 000x xx11b; depending on I/O dedication.

These are not internal CPU registers and must be accessed by reading and writing to the relevant memory locations. Refer toTable 1- Memory Map for the respective addresses and reset values.

4.1.2.2 Functional Description

Each I/O pin may be programmed independently as an analog input if the port features analog capabilities, as a digital input or a digital output with various variants, using the corresponding register bits. When programmed as a digital input, a pull-up or a pull-down resistor can, if present, be activated by software. Only when enabling the pull-up, can an interrupt function be programmed by software. When programmed as an output, the I/O pin can be programmed to operate either in push-pull or in open-drain mode.

The interrupts generated by a port (active low) are “ORed” to a single interrupt line that can be routed to a CPU interrupt.

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ST7285C

I/O PORTS (Cont’d) Figure 13. Generic I/O Circuitry

PAD

FROM OTHER BITS

DR SEL

OR SEL

DDR SEL

PUR SEL

PUR

DDR

DAT A BUS

INTERRUPT

M U

SIGNAL FROM ALTERNATE

TRIGGER ENABLE

PAD_TRIG

ANALOG

SWITCH

ANALOG ENABLE

COMMON ANALOG RAIL

from

ADC

M U X

ALTERNATE FUNCTION ENABLE

CONFIGURATION

DECODER

ALTERNATE FUNCTION ENABLE

CONFIGURATION

DECODER

FUNCTION

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ST7285C

I/O PORTS (Cont’d)

4.1.2.3 Operating Modes

All I/O pins may be configured as inputs or outputs by programming the corresponding bits of the DR, DDR, OR and PUR memory-mapped registers. Table 6 illustrates the available operating modes. During Reset, DR, DDR, OR and PUR are initialized to a Low level.

Table 6. I/O Operating Modes

Note:

(1) This state can add static current consumption.

– Input Mode

In input mode, both the analog multiplexer and the port buffer are switchedto a high impedance state.

To avoid ringing with slowly rising or falling input signals and to increase noise immunity, the inputs are equipped with Schmitt-triggers.

The state of the pin is readable through the Data Register. The pin state is read directly from the Schmitt Trigger’s output and not from the Data Register.

There are four different input modes, as illustrated in Table 6.

Note: Pull-up and pull-down devices are not implemented by means of linear resistors, but by means of resistive transistors.

– Interrupt function

The interrupt signals of all activated bits are NANDed together, so that whenever at least one of the activated inputs goes low, the port’s common interrupt output will go high in order to activate the CPU interrupt input.

– Output Mode

In output mode, the port output buffer is activated and drives the output according to the content of

the data register, DR. In this mode, the analog multiplexer, when present, is switched to high impedance and the interrupt is disabled.

Data written to the DR is directly copied to the output pins. A read operation of DR will be directly performed from the DR register, so that the output data stored in DR is readable, regardless of the logic levels at the output pin due to output loading. There are three different output modes for the standard I/O pins as illustrated inTable 6.

– Alternate function

Alternate functions take priority over standard I/O programming; if a peripheral needs to use a pad, the alternate function is automatically activated.

The signal from the peripheral is output to the pad (automatically configured in this case in push-pull or open drain modes without pull-up and pulldown), and controlled directly by the peripheral.

The signal to be input to the peripheral from the pad is taken after the schmitt trigger and is controlled directly by the peripheral. In this case, the pin’s state is readable as in Input Mode by addressing the Data Register and by configuring the PAD in Input Mode (DDR=0).

– Analog Input Mode

In analog input mode (activated by the ADC), the analog multiplexer is activated and switches the analog voltage present on the selected pin (pins PA0 to PA7) to the common analog rail. The common analog rail is connected to the Analog to Digital converter (see Section4.6) input. It is not recommended to change the voltage level or loading on any port pin while conversion is in progress. Furthermore it is not recommended to have clocking pins located close to a selected analog pad.

WARNING: Before activating the Analog Input Mode, the I/O state must be set to: INPUT, NO PULL-UP, NO INTERRUPT (DDR = 0, OR = 0, PUR = 1) The alternate function must not be activated as long as the pad is configured as Input with Interrupt, in order to avoid generating spurious interrupts. Analog input mode is only implemented for pins PA0 to PA7. The analog input voltage level must be within the limits stated in the Absolute Maximum Ratings.

DDR OR PUR Mode Option

0 0 0 input pull-up, no interrupt 0 0 1 input no pull-up, no interrupt 0 1 0 input pull-up, interrupt 0 1 1 input pull-down, no interrupt 1 0 0 output open-drain, pull-up 1 0 1 output open-drain, no pull-up 1 1 0 output RESERVED

(1)

1 1 1 output

push-pull, nopull-up, no pull-down

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ST7285C

I/O PORTS (Cont’d)

4.1.3 I/O Port Implementation

On the ST7285C, the pull down is always absent, the pull up exists only where an interrupt facility is present (Ports C4, C5, D4, D5, F0, F1, F2, F3, G3). On port A, the analog inputs are directly controlled by the ADC.The I/O port register configurations are reduced to the following.

4.1.3.1 Ports A0-A7, B0-B7, C0-C3, C6, C7, D0D3, D6, D7,E0-E7, F4-F7, G0-G2, G4-G7, H0-H5

These ports do not offer interrupt capabilities.

Note: Open drain I/O is implemented on I2C pins (pins 19 and 20) and high voltage pins (PH3/4/5). The design uses special I/O devices without P channel, thus forbidding the push pull configuration.

In this case there is neither pull up register nor option register. These registers do not exist and so cannot be read or written to.

4.1.3.2 Ports C4, C5, D4, D5, F0-F3, G3

These ports offer interrupt capabilities.

In this case there is no pull up register since the pull-up is present only when the interrupt feature is selected. This register does not exist and so cannot be read or written to.

Switching these I/O ports from one state to another should be done in such a sequence as to prevent unwanted side effects. Recommended safe transitions are illustrated inFigure 14. Other transitions are potentially risky and should be avoided, since they are likely to present unwanted side-effects such as spurious interrupt generation.

Figure 14. Recommended I/O State Transition Diagram

DDR MODE OPTION

0 input no pull-up, no pull-down, no interrupt 1 output push-pull (or open drain: see note)

DDR OR

MOD

OPTION

0 0 input

no pull-up, no pull-down,

no interrupt 0 1 input interrupt, pull-up 1 0 output open-drain, no pull-up

1 1 output

push-pull, no pull-up,

no pull-down

110001

Interrupt pull-up

push-pull no pull-up

open-drain no pull-up

no pull-down

INPUT

OUTPUT

no pull-up no interrupt

INPUT

no pull-down (Reset state)

= DDR, OR

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ST7285C

4.2 SERIAL COMMUNICATIONS INTERFACE

4.2.1 Introduction

The Serial Communications Interface (SCI) offers a flexible means of full-duplex data exchange with external equipment requiring an industry standard NRZ asynchronous serial data format. The SCI offers a very wide range of Baud rates thanks to the presence of two Baud rate generator systems: the first is of conventional type and yields common communications Baud rates with standard oscillator frequencies; the second features a programmable prescaler capable of dividing the input frequency by any factor from 1 to 255, thus offering a very wide range of Baud rates even with nonstandard oscillator frequencies. Transmitter and Receiver circuits are independent and can operate at different Baud rates; indeed, each can select either type of Baud rate generator. External connections are by means of two I/O pins: TDO (Port PB0) for the Transmit Data output and RDI (Port PB1) for the Receive Data input.

4.2.2 Features

– Full duplex, asynchronous communications – NRZ standard format (Mark/Space) – Dual Baud rate generator systems – Independently programmable transmission and

reception Baud rates – Separate Transmit and Receive Baud rates – Programmable word length (8 or 9 bits) – Receive buffer full, Transmit buffer empty and

End of Transmission flags – Receiver wake-up function by the most signifi-

cant bit or by idle line – Muting function for multiprocessor configurations –Separate enable bitsforTransmitter andReceiver – Noise, Overrun and Frame Error detection – Four interrupt sources with flags – Overall accuracy better than 1% of Baud rate.

4.2.3 Serial Data Format

Serial data is transmitted and received as frames comprising the following elements:

– An Idle Line in the ”high” state prior to transmis-

sion or reception. – A Start bit inthe ”low” state, denoting the start of

each character. – Character dataword (8 or 9 bits), least significant

bit first.

– A Stop bit in the ”high” state, indicating that the

frame is complete.

Word length may be selected as being either 8 or 9 bits by programming the M bit in the SCCR1 control register.

An Idle Line condition is interpreted on receiving an entire frame of ”ones”.

A Break is interpreted on receiving ”zeros” for some multiple of the frame period.

4.2.4 Data Reception and Transmission

The following description is best read with reference to the SCI Block Diagram illustrated in Figure 1, where it will be noted that the SCDR data register is shown as two separate registers, one for transmitted data and the other for received data.

The Serial Communications Data Register (SCDR) performs a dual function (Read And Write),since it accesses two separate registers, one for transmission (TDR) and one for reception (RDR). The TDR register provides the data interface between the internal bus and the output shiftregister for data to be transmitted, while the RDR register provides an interface between the input shift register and the internal bus for incoming data.

When the SCDR is read, the RDR is accessed and its contents are transferred to the data bus. The RDRF (RDR Full Flag) in the SCSR register is set to ”1” as soon as the word in the receiver shift register is transferred to the RDR register.

When the SCDR is written to, the data word is transferred to the TDR register. The TDRE flag (TDR empty) in the SCSR register is set to ”1” as soon as the word in the TDR is transferred to the transmit shift register.

Incoming data is received in a serial shift register and then transferred to a parallel Receive Data Register (RDR) as a complete word, thus allowing the next incoming character to be received in the shift register while the current character is still in the RDR.

Oversampling techniques are used for data recovery by discriminating between valid incoming data and noise.

4.2.5 Receiver Muting and Wake-up Feature

In multiprocessor configurations it is often desirable that only the intended message recipient should actively receive the full message contents, thus reducing redundant SCI service overheads for all non addressed receivers. Communications protocols in such configurations generally issue the recipient address as a message header.

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Each receiving device decodes this address header under program control and all non addressed receivers may be placed in a sleep mode by means of the Muting function, thus avoiding the message contents from generating unnecessary requests for service. This is achieved by inhibiting all reception flags and interrupt generation when Muting is enabled. A muted receiver may be reawakened in one of two ways: by Idle Line detection or by Address Mark detection. The wake-up method may be programmed by programming the WAKE bit in the SCCR1 register.

Receiver wake-up by Idle Line detection takes place as soon as the Receive line is recognised as being idle. An Idle Line condition is detected upon receiving 10 or 11 consecutive ”ones”, depending on whether a word has been defined as comprising 8 or 9 data bits. This wake-up method is selected by programming the WAKE bit to ”0”.

Receiver wake-up by Address Mark detection takes place on receiving a ”1” as the most significant bit of a word, thus indicating that the message is an address. This wake-up method is selected by programming the WAKE bit to ”1”.

4.2.6 Baud Rate Generation

The following description is best read with reference to the SCI Baud Rate and External Prescaler Diagram illustrated in Figure 2.

The CPU Clock is first divided by 16 by the first divisor block, then again divided by the division factor selected for the first prescaler, indicated by PR. This division factor can be selected to be 1, 3, 4 or 13, depending on the setting of the SCP0 and SCP1 bits (bits 6 and 7) in the SCBRR register (refer to the register description). The output from the first prescaler will thus be the CPU Clock frequency divided by 16, 48, 64 or 208. This master clock is available both to the conventional Baud Rate Generator and to the External Prescaler.

The conventional Baud Rate Generator is enabled by setting the relevant section (RX or TX) of the External Prescaler to 00h. In this case the master clock frequency is further divided by 1, 2, 4, 8, 16, 32, 64 or 128, depending on the settings of bits SCT0, SCT1 and SCT2 in the case of the transmitter, and SCR0, SCR1 and SCR2 in the case of the receiver (refer to the SCBRR register description).

If the External Prescaler Receive or Transmit Baud Rate Register, PSBRT or PSBRR is set to a value other than zero, that section of the prescaler

will be operational in place of the conventional Baud Rate Generator. The output clock rate sent to the transmitter or to the receiver will be the output from the first prescaler divided by a factor ranging from 1 to 255 set in the External Prescaler Receive or Transmit Baud Rate Register. As can be seen the External Prescaler option gives a very fine degree of control on the Baud rate, whereas the conventional Baud Rate Generator retains industry standard software compatibility.

4.2.7 SCI Register Overview

The registers described in the following paragraphs allow full control of the various features and parameters of the Serial Communications Interface. Refer also to the Memory Map.

4.2.7.1 Data Register (SCDR)

Address: 0051h — Read/Write Reset Value: XXh Contains the Received or Transmitted data char-

acter, depending on whether it is read or written to.

4.2.7.2 Control Register 1 (SCCR1)

Address: 0053h — Read/Write Reset Value: XXh Contains bits to select the desired word length and

the wake-up mode.

Bit-7 = R8

Receive Data Bit 8

If bit M is set at one, R8 will be used to store the 9th bit on reception.

Bit-6 = T8

Transmit Data Bit 8

Used to store the 9th data bit of the transmitted word, when 9-bit word length is selected (bit M set to ”1”).

Bit-4 = M

Word Length

Determines the word length: 0 = 1 Start bit, 8 Data bits, 1 Stop bit 1 = 1 Start bit, 9 Data bits, 1 Stop bit

Bit-3 = WAKE

Wake-Up Method

1 = Address Mark 0 = Idle Line

76543210

R8 T8 - M WAKE - - -

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4.2.7.3 Control Register 2 (SCCR2)

Address: 0054h — Read/Write Reset Value: 00h Contains four control bits which allow interrupts

generated by TDR Empty, Transmit Complete, RDR Full and Idle Line to be enabled or disabled.

Also contains four control bits to enable or disable Transmission, Reception, Receiver Wake-Up and Send Break.

Bit-7 =

TIE

Transmitter Interrupt Enable

Authorizes an interrupt when set at one and when the TDRE (transmission register empty) flag is set to “1” indicating that the last word has been transmitted. When TIE is at zero this interrupt is disabled.

Bit-6 = TCIE

Transmission Complete Interrupt En-

able

This bit setto “1” enables an interrupt when theTC flag (transmission competed) changes to “1”. When TCIE is at “0” this interrupt is disabled.

Bit-5 = RIE

Receiver Interrupt Enable

Authorizes an interrupt when set to “1” and when either the RDRF (Receive Data Register Full) flag or the OR (Overspeed on Reception) flag is set to “1”, indicating that the last word has been transmitted. When TIE is set to “0”, this interrupt is disabled.

Bit-4 = ILIE

Idle Line Interrupt Enable

This bit at “1” enables an interrupt if the IDLE flag changes to “1” (which corresponds to an idle line on reception). The interrupt cannot occur if the IDLE bit is at “0”.

Bit-3 =

Transmitter Enable

This bit at “1” enables the transmitter. At start-up, the transmitter sends a preamble (ten or eleven ones). During transmission, a “0” pulse on the TE bit (“0” followed by “1”) sends a preamble after the current word. Setting the TE bit to “0” switches the output line to a high impedance state at the end of the word currently being transmitted.

Bit-2 = RE

Receiver Enable

The RE bit at “1” enables the receiver which begins searching for a START bit. The RE bit at “0” disables the receiver and resets the associated status bits to “0” (RDRF, IDLE, OR, NF and FE).

Bit-1 = RWU

Receiver Wake-Up

The RWU bit at “1” mutes the receiver. The wakeup mode is determined by the WAKE bit (bit 3 in SCCR1). As long as RWU remains at “1”, the flags relating to the receiver cannot rise to “1”. Writing “0” to RWU forces an exit from the muted state. As soon as the wake-up sequence is recognized, the RWU bit is forced to “0”. If the wake-up selected mode corresponds to the reception of a preamble, the RWU bit cannot be set to “1” as long as the reception remains idle. If the selected wake-up mode corresponds to the reception of a “1” on the most significant bit, the reception of this particular word wakes up the receiver and sets the RDRF flag to “1”, which allows the receiver to receive this word normally and to use it as an address word.

Bit-0 = SBK

Send Break

This bit set to “1” tells the transmitter to send a whole number of BREAKS (all bits at “0” including the stop bit). At the end of the last BREAK the transmitter inserts an extra “1” bit in order to acknowledge the START bit. If the SBK bit is set to “1” and then to “0”, the transmitter will send a BREAK word at the end of the current word.

4.2.7.4 Status Register (SCSR)

Address: 0050h — Read Only Reset Value: 1100 0000b Contains four flags which denote conditions which

can lead to interrupts if the corresponding bits of SCCR2 are set: TDR Empty, Transmit Complete, RDR Full and Idle Line. These flags are used for management of the SCI interrupt system.

Also contains three flags which indicate error conditions due to Overrun, Noise and Framing.

Bit-7 =TDRE

Transmit Data Register Empty

Indicates that the content of the transmission data register has been transferred into the shift register. If the TDRE bit is at “0”, it indicates that the transmission has not yet occurred and that a write operation into the data register would overwrite previous data. The TDRE bit is reset to “0” by an SCSR access followed by a write operation into the transmission data register. Data will not be transferred to the shift register as long as the TDRE bit is not reset to “0”.

Bit-6 =

Transmission Complete

76543210

TIE TCIE RIE ILIE TE RE RWU SBK

76543210

TDRE TC RDRF IDLE OR NF FE -

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The TC bit is automatically set to “1” when transmission of a frame containing Data, a Preamble or a Break is complete, if:

– TE = ”1”, TDRE = ”1”, no word is currently being

transmitted and no preamble or BREAK is await-

ing transmission. – TE = ”0” and the current word or preamble or

BREAK has been transmitted The TC bit is aflag indicating that one of the above

sequences has occurred. This bit is reset to “0” by an access to the SCSR followed by a write operation into the data register or when TDRE is reset to “0”. Transmitter operation is in no way modified by the status of this bit.

Bit-5 =

RDRF

Received Data Ready Flag

This bit, when set to “1”, indicates that the content of the RDR has been transferred into the SCDR. If a Frame Error or Noise has been detected during reception, the corresponding flags will be set.

The RDRF bit is reset to “0” by an access to the SCSR followed by a data register read operation.

Bit-4 = IDLE

Idle Line Detect

When the idle line detect bit is set it indicates that the receiver idle line is detected (receipt of a minimum number of ones (10 when M=0, 11 when M=1) to constitute the number of bits in the frame format. This allows a receiver that is not in the wake-up mode to detect the end of a message or the preamble of a new message or to re-synchronize with the transmitter. The IDLE bitis cleared by accessing the SCSR (with idle set) followed by a read of the data register. The IDLE bit will not be set again until the RDRF bithas been set itself (i.e. a new idle line occurs). The IDLE bit is not set by an idle line when the receiver wakes up from wake up mode.

Bit-3 =

Overrun Error

This bit is set to “1”, when the word currently being received in the shift register is ready to be transferred into the data register while the latter is already full (RDRF=”1”). All transfers will remain disabled as long as RDRF remains at “1”. Data register content will not be lost but the shift register will be overwritten. The OR bit is reset by an access to the SCSR followed by a data register read operation.

Bit-2 = NF

Noise Flag

This bit is set to “1” when noise is detected on an acknowledge START bit or a data bit or a stop bit. The NF is set to “1” when the noise is detected at the rising edge of RDRF and is representative of the word present in the data register. This bit does

not generate interrupts as it appears at the same time as RDRF which itself generates an interrupt. The NF bit is set to “0” by a SCSR read operation followed by a data register read operation.

Bit-1 =

Framing Error

This bit is set to “1” when the STOP bit is not recognized on reception at the expected moment, following either a de-synchronization, excessive noise or when a BREAk is received. The word will, however still be transferred to the data register. As in the case of the NF bit, the FEW bit does not generate an interrupt as it appears at the same time as RDRF bit. If the word currently being transferred causes both frame error and reception overspeed, it will be transferred and only the OR bit will be set to “1”. The FE bit is reset to “0” by a SCSR read operation followed by a data register read operation.

Bit-0 =

Unused

4.2.7.5 Baud Rate Register (SCBRR)

Address: 0052h — Read/Write Reset Value: 00X----Xb Contains two bits for selection of the first prescaler

factor, three bits for selection of the transmitter rate divisor and three bits for the receiver rate divisor.

Bit-7 =SCP1

First prescaler MSB

Bit-6 =SCP0

First prescaler LSB

These 2 prescaling bits allow several standard clock division ranges:

Bit-5 =SCT2

Transmitter rate divisor MSB

Bit-4 =SCT1

Transmitter rate divisor NSB

Bit-3 =

SCT0

Transmitter rate divisor LSB

These 3 bits, in conjunction with the 2 previous bits define the total division applied to the bus clock to yield the transmit rate clock in conventional Baud Rate Generator mode.

76543210

SCP1 SCP0 SCT2 SCT1 SCT0 SCR2 SCR1 SCR0

SCP1 SCP0 PR Prescaling factor

00 1 01 3 10 4 11 13

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This TR factor is used only when the PSBRT fine tuning factor is equal to 0; otherwise, TR is replaced by the PSBRT dividing factor.

Bit-2 = SCR2

Receiver rate divisor MSB

Bit-1 = SCR1

Receiver rate divisor NSB

Bit-0 =

SCR0

Receiver rate divisor LSB

These 3 bits, in conjunction with the 2previous bits define the total division applied to the bus clock to yield the receive rate clock in conventional Baud Rate Generator mode..

This RR factor is used only when the PSBRR fine tuning factor is equal to 0; otherwise, RR is replaced by the PSBRR dividing factor.

4.2.7.6 External Receive Prescaler Division Register (PSCBRR)

Address: 0055h — Read/Write Reset Value: 00h Allows setting of the External Prescaler rate divi-

sion factor for the receive circuit.

When the register is set to 00h, the conventional Baud Rate Generator is used for the receive circuit, otherwise the master clock frequency is divided by the binary factor set in the PSCBRR register (in the range 1 to 255).

4.2.7.7 External Transmit Prescaler Division Register (PSCBRT)

Address: 0057h — Read/Write Reset Value: 00h Allows setting of the External Prescaler rate divi-

sion factor for the transmit circuit.

When the register is set to 00h, the conventional Baud Rate Generator is used for the transmit circuit, otherwise the master clock frequency is divided by the binary factor set in the PSCBRTregister (in the range 1 to 255).

SCT2 SCT1 SCT0 TR dividing factor

000 1 001 2 010 4 011 8 100 16 101 32 110 64 1 1 1 128

SCR2 SCR1 SCR0 RR dividing factor

000 1 001 2 010 4 011 8 100 16 101 32 110 64 1 1 1 128

76543210

PRBR7PRBR6PRBR5PRBR4PRBR3PRBR2PRBR1PRBR

76543210

PTBR7PTBR6PTBR5PTBR4PTBR3PTBR2PTBR1PTBR

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SERIAL COMMUNICATIONS INTERFACE(Cont’d) Figure 15. SCI Block Diagram

FLAG

CONTROL

RECEIVE

DATA

RECEIVE

DATA

SHIFT

WAKE

UNIT

RECEIVER

CONTROL

TRANSMIT

DATA

SHIFT

TRANSMIT

DATA

TDO

SCCR2

RWU

SBK

ILIE

RIE

TCIE

TIE

TDRETCRDRFIDLEORNFFE

46705

SCSR

TRANSMIT

CONTROL

R8T8

SCCR1

RDI

INTERNAL B US

SCI INTERRUPT

WAKE

TRANSMIT CLOCK

RECEIVE CLOCK

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SERIAL COMMUNICATIONS INTERFACE(Cont’d) Figure 16. SCI Baud Rate and External Prescaler Block Diagram

RECEIVER RATE CONTROL

TRANSMITTER RATE CONTROL

TRANSMITTER

RECEIVER

PSCBRT

SCBRR

PSCBRR

EXTERNAL PRESCALER RECEIVER RATE CONTROL

EXTERNAL PRESCALER TRANSMITTER RATE CONTROL

EXTERNAL PRESCALER

CPU CLOCK

Divide by16Divide by

CONVENTIONAL BAUD RATE

GENERATOR

CLOCK

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4.3 16-BIT TIMER

4.3.1 Introduction

One or more Timers may be present in the MCU, depending on product specification. Please refer to the Block Diagram to ascertain available product resources, and to the Memory Map for register addresses.

Each timer consists of a 16-bit free-running counter driven by a programmable prescaler, as well as the control logic required to implement two input capture and two output compare registers. The timer may be used for a variety of purposes, amongst which pulse length measurement of up to two input signals and generation of up to two output waveforms (e.g. PWM). The Timer Block Diagram is illustrated in Figure 1.

Pulse lengths and waveform periods can vary from a few microseconds to many seconds, thanks to the programmable prescaler. When running with a 4MHz internal CPU clock, the timer can have a resolution of 0.5, 1 or 2µs, depending on the setting of the clock control bits in the Timer Control Register (TCR2). A software selectable external clock input pin is available.

Since the timer has a 16-bit architecture, each of its specific functional blocks is associated with a register pair. These registers contain the high order byte and the low order byte respectively of the related function. Access to the high order byte inhibits the associated timer function until the low order byte is also accessed.

Correct software procedures should set bit ‘I’ of the Condition Code Register before accessing the high order byte to prevent an interrupt from occurring between accesses to the high and low order bytes of any register.

In normal operating mode, reading the MSB of the Input Capture register inhibits Input Capture until the LSB is read. This mechanism allows Input capture to be disabled when the pin is connected to an I/O bit.

When the Pulse Width Modulation (PWM) and One Pulse Mode (OPM) features are selected together, the PWM mode is the only active one.

4.3.2 Counter

The key element of the Programmable Timer is a 16-bit free running counter and its associated register. The counter is preceeded by a prescaler which divides the internal clock by two, four or eight, depending on the setting of the clock control bits of the Timer Control Register (TCR2), as illustrated in Table 1 below.

Table 7. Clock Control Bits

Software can read the counter at any time without affecting its value, either from the Counter Registers or from the Alternate Counter Registers. The only difference between these two read-only register pairs is the way the overflow flag (TOF) is handled during a read sequence.

A read sequence where only the least significant byte of the free running counter is read (from either the Counter Register or the Alternate Counter Register), will receive the LSB of the count value at the time of the read.

A read of the most significant byte (from either the Counter Register or the Alternate Counter Register) simultaneously returns the MSB of the count value and causes the LSB to be transferred to a buffer. The buffered value remains unchanged until the 16-bit read sequence is completed, even if the user reads the MSB several times. The read sequence is completed by reading the LSB, which actually returns the buffered value.

As shown in Figure 2, Figure 3 and Figure 4, the free-running counter is set to FFFCh on Reset. During a Power-On Reset (POR) cycle, the counter is loaded with FFFCh and begins running.

CC1 CC0 Clock Divisor

00 4 01 2 10 8 1 1 External Clock

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16-BIT TIMER(Cont’d) Figure 17. Timer Block Diagram

MCU-PERIPHERAL INTERFACE

COUNTER

ALTERNATE

OUTPUT

COMPARE

OUTPUT COMPARE

EDGE DETECT

OVERFLOW

DETECT

CIRCUIT

1/2 1/4

1/8

8-bit

buffer

ST7 INTERNAL BUS

LATCH1

OCP1

ICP1

TCLK

CPU CLOCK

TIMER INTERRUPT

ICF2ICF1 000OCF2OCF1 TOF

PWMOC1E

EXEDG

IEDG2CC0CC1

OC2E

OPMFOLV2ICIE OLVL1IEDG1OLVL2FOLV1OCIE TOIE

ICP2

LATCH2

OCP2

8low

8 high

16 16

CC1 CC0

TCR1

TCR2

TSR

888

high

low

high

low

EXEDG

PORT

TIMER INTERNAL BUS

CIRCUIT1

EDGE DETECT

CIRCUIT2

CIRCUIT

OUTPUT COMPARE REGISTER

INPUT

CAPTURE

INPUT CAPTURE REGISTER

CC1 CC0

16 BIT

FREE RUNNING

COUNTER

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16-BIT TIMER(Cont’d)

When the counter rolls over from FFFFh to 0000h, the Timer Overflow flag (TOF) of the Timer Status Register (TSR) is set. A timer interrupt is then generated if the TOIE enable bit of the Timer Control Register (TCR1) is set, provided the I bit of the CCR is cleared. If one of these conditions is false, the interrupt remains pending to be issued as soon as they are both true. The interrupt request is cleared by reading TSR while TOF is set, followed by an access (read or write) to the LSB of the Counter Register.

The TOF flag is not affected by accesses to the Alternate Counter Register. This feature allows simultaneous use of the overflow function and reads of the free running counter at random times (for example, to measure elapsed time) without risking to clear the TOF flag erroneously. Accesses to the timer without the intention of servicing the TOF flag should therefore be performed to the Alternate Counter Register while only the TOF service routine accesses the Counter Register.

The free running counter can be reset under software control, by writing to the LSB of the Counter Register or of the Alternate Counter Register. The counter and the prescaler are then configured to their reset conditions. This reset also completes any 16-bit access sequence. All flags and enable bits are unchanged.

The value in the counter registers repeats every 131,072, 262,144, or 524,288 internal processor clock cycles,depending on the clock control option selected in TCR2. As shown in the timing diagrams, the counter increment is triggered by a falling edge of the CPU clock.

The timer is not affected by WAIT mode. In HALT mode, the counter stops counting until the mode is exited. Counting then resumes from the previous count (MCU awakened by an interrupt) or from the reset count (MCU awakened by a Reset).

4.3.3 External Clock

When the external clock is selected by setting the relevant clock control bits in TCR2, the counter clocks on each external clock rising edge, if EXEDG in TCR2 is set, or the falling edges if reset, and is synchronised with the falling edge of the internal CPU clock.

At least four falling edges of the CPU clock must occur between two consecutive active edges of the external clock; thus the external clock frequency must be less than a quarter of the CPU clock frequency.

The parasitic pulses generated by the EXTEDG and EXTCLKE transitions are filtered during two clock periods, so the manipulation of the external clock control bits must occur before or after two internal clock periods.

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16-BIT TIMER(Cont’d) Figure 18. Timer Timing Diagram, internal clock divided by 2

Figure 19. Timer Timing Diagram, internal clock divided by 4

Figure 20. Timer Timing Diagram, internal clock divided by 8

CPU CLOCK

FFFD FFFE FFFF 0000 0001 0002 0003

INTERNAL RESET

INTERNAL TIMER CLOCK T10

COUNTER REGISTER

OVERFLOW FLAG TOF

FFFC FFFD 0000 0001

CPU CLOCK

INTERNAL RESET

INTERNAL TIMER CLOCK T10

COUNTER REGISTER

OVERFLOW FLAGTOF

INTERNAL TIMER CLOCK T00

CPU CLOCK

INTERNAL RESET

INTERNAL TIMERCLOCK T10

COUNTER REGISTER

OVERFLOW FLAG TOF

FFFC FFFD

0000

INTERNAL TIMERCLOCK T00

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4.3.4 Input Capture

The timer features two input capture registers and an input capture interrupt enable bit.

The Input Capture Registers (ICR1 and ICR2) each consist of two 8-bit registers: the most significant byte registers (ICHR1 and ICHR2), and the least significant byte registers (ICLR1 and ICLR2).

In the following description, the variableimay represent 1 or 2.

ICRiis a read-only registers used to latch the value of the free running counter after a defined transition is sensed by the input capture edge detector at pin ICAPi. This transition is software programmable through the IEDGibit of the Timer Control Register (TCRi). When IEDGiis set, a rising edge triggers the capture; when IEDGiis low, the capture is triggered by a falling edge.

When an input capture occurs, the ICFiflag in the Timer Status Register (TSR) is set. An interrupt is requested if the interrupt enable bit, ICIE, of TCR1 is set, provided the I bit of the CCR is reset. Otherwise, the interrupt remains pending until both conditions become true. It is cleared by reading the TSR followed by a read or write of the LSB of ICRi.

The result stored in ICRiis one more than the value of the free running counter on the rising edge of the internal processor clock preceding the active transition on the ICAPipin (see Figure 5). This delay is required for internal synchronization. Therefore, the timing resolution of the input capture system is one count of the free running counter, i.e. 2, 4 or 8 internal clock cycles, depending on the clock control bits of TCR2.

The free running counter is transferred to ICRion each proper signal transition regardless of whether the Input Capture Flag ICFiis set or cleared. The ICRialways contains the free running counter value which corresponds to the most recent input capture.

After reading the MSB of ICRi, transfer of input capture data is inhibited until the LSB is also read. This implies that the minimum pulse period is determined by the time required to respond to the interrupt and to execute the service routine.

Reading ICLRidoes not inhibit transfer of counter data. The minimum pulse period is determined by the time required to read the least significant byte and to perform necessary actions. There is no conflict between reading ICRiand the running counter transfer, since they occur on opposite clock edges as shown in Figure 5.

ICRiis undetermined on power-on, and is not affected by an external Reset. Hardware circuitry must provide protection against generating an undesired input capture when changing the edge sensitivity option of the ICAPipin by programming the IEDGibit.

During HALT mode, if at least one valid input capture edge occurs on the ICAPipin, the input capture detection circuitry is armed. This does not set any timer flags, and does not ”wake-up” the MCU. If the MCU is awoken by an interrupt, the input capture flag will be active, and data corresponding to the first valid edge during HALT mode will be present. If HALT mode is exited by a Reset, the input capture detection circuitry is reset and thus, any active edge that occurred during HALT mode will be lost.

Figure 21. Input Capture Timing Diagram

FF01 FF02 FF03

FF03

CPU CLOCK ÷2 CPU CLOCK ÷4

CPU CLOCK ÷8 INTERNAL CLOCK T10 INTERNAL CLOCK T11

COUNTER REGISTER

ICAPi PIN

ICAPi FLAG

ICAPi REGISTER

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16-BIT TIMER(Cont’d)

4.3.5 Output Compare

Two output compare registers are present: Output Compare Register 1 and Output Compare Register 2 (OCR1 and OCR2). These registers can be used for several purposes, such as controlling an output waveform or indicating when a period of time has elapsed. The OCMPipin is associated with the Output Compareifunction (i= 1 or 2).

The Output Compare Registers are unique in that all bits are readable and writable and are not affected by the timer hardware or by Reset. If a compare function is not used, the two bytes of the corresponding Output Compare Registers can be used as general purpose storage locations.

4.3.5.1 Output Compare Registers

The Output Compare Registeri(OCRi) is a 16-bit register, which is made up of two 8-bit registers: the most significant byte register (OCHRi) and the least significant byte register (OCLRi).

In this section, the index,i, may be 1 or 2. The content of OCRiis compared with the content

of the free running counter once during every timer clock cycles, i.e. once every 8, 4 or 2 internal processor clock periods or 2 external clock periods according to the clock control bits of the Timer Control Register (TCR2). If match is found, the Output Compare Flag OCFiof the TSR is set and the Output Level bit (OLVLi) of the TCR1 is clocked to the OCMPipin (see output compare timing diagrams Figure 6, Figure 7, Figure 8). OLVLiis copied to the corresponding output level latch and hence, to the OCMPipin regardless of whether the Output Compare Flag (OCFi) is set or not. The value in the OCRiand the OLVLibit should be changed af-

ter each successful comparison in order to control an output waveform or establish a new elapsed timeout.

An interrupt accompanies a successful output compare if the corresponding interrupt enable bit OCIE of the TCR1 is set, provided the I-bit of the CCR is cleared. Otherwise, the interrupt remains pending until both conditions are true. It is cleared by a read of TSR followed by an access to the LSB of the OCRi.

After a processor write cycle to the OCHRiregister, the output compare function is inhibited until the OCLRiis also written. Thus, the user must write both bytes if the MSB is written first. A write made to only the LSB will not inhibit the compare function. The minimum time between two successive edges on the OCMPipin is a function of the software program and the clock control bits of the TCR2.

The OCMPioutput latch is forced low during reset and stays low until valid compares change it to a high level. Because the OCFiflag and the OCR

are undeterminate at power-on and are not affected by an external reset, care must be exercise when initiating the output compare function with software. The following procedure is recommended to prevent the OCFiflag from being set between the time it is read and the write to OCRi:

– Write to OCHRi(further compares are inhibited). – Read the TSR (first step of the clearance of OC-

Fi, which may be already set).

– Write to OCLRi(enables the output compare

function and clears OCFi).

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16-BIT TIMER(Cont’d) Figure 22. Output Compare Timing Diagram, internal clock divided by 8

Figure 23. Output Compare Timing Diagram, internal clock divided by 4

Figure 24. Output Compare Timing Diagram, internal clock divided by 2

INTERNAL CPU CLOCK

INTERNAL TIMER CLOCK T01

INTERNAL TIMER CLOCK T11

COUNTER

FFFC FFFD

FFFC

COMPARE REGISTER

COMPARE REGISTER LATCH

OUTPUT REGISTER FLAG OCFI AND OCMPI PIN

INTERNAL CPU CLOCK

INTERNAL TIMER CLOCK T01

INTERNAL TIMER CLOCK T11

COUNTER

COMPARE REGISTER

COMPARE REGISTER LATCH

OUTPUT REGISTER FLAGOCFI AND OCMPI PIN

FFFC FFFD FFFE

CPU

writes

FFFD

INTERNAL CPU CLOCK

INTERNAL TIMER CLOCK T01

INTERNAL TIMER CLOCK T11

COUNTER

COMPARE REGISTER

COMPARE REGISTER LATCH

OUTPUT REGISTER FLAG OCFI AND OCMPI PIN

CPU

writes

FFFF

FFFD FFFD FFFE FFFF 0000FFFC

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16-BIT TIMER(Cont’d)

4.3.5.2 Forced Compare Mode

The main purpose of the Forced Compare mode is to facilitate fixed frequency generation.

In this sectionimay represent 1 or 2. When the Forced Output Levelibit (FOLVi)of

TCR1 is written to 1, OLVLiis copied to the OCMP

pin. To provide this capability, internal logic allows a single instruction to change OLVLiand causes a forced compare with the new value of OLVLi.OCF

is not affected, and thus no interrupt request is generated.

4.3.5.3 One Pulse Mode

The One Pulse mode enables the generation of a pulse on the occurence of an external event and is programmed via the OPM bit in the TCR2 register.

The trigger event is applied to the Input Capture1 pin (ICAP1); the active edge of the event is flagged by the IEDG1 bit in TCR1.

Then, on an event on ICAP1, the counter is initialized to FFFCh and OLVL2 is loaded on the output compare 1 pin (OCMP1); when the value of the counter is equal to the value of the contents of OCR1, the OLVL1 bit is output on the Output Compare 1 pin (OCMP1). No interrupt is generated. (See Figure 9).

4.3.5.4 Pulse Width Modulation Mode

This mode is similar to the One Pulse mode, in which the external event is replaced by the Output Compare 2 event; this mode is programmed via the PWM bit in the TCR2 register.

OCR1 then contains the length of the pulse, while OCR2 contains the value of the period; the Output Compare 2 event causes the counter to be initialized to FFFCh (See Figure 10). No interrupt is generated

Figure 25. One Pulse Mode Timing, IEDG1=1; OCR1=2ED0h

Figure 26. Pulse Width Modulation Mode Timing, OCR1=2ED0h, OCR2=34E2

COUNTER

....

FFFC FFFD FFFE 2ED0 2ED1 2ED2

2ED3

FFFC FFFD

OLVL2

OLVL2OLVL1

ICAP1

OCMP1

compare1

COUNTER

34E2

FFFC FFFD FFFE 2ED0 2ED1 2ED2 34E2 FFFC

OLVL2

OLVL2OLVL1

OCMP1

compare2 compare1 compare2

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16-BIT TIMER(Cont’d)

4.3.6 Timer Registers

As can be seen from the Memory Map, each Timer is associated with three control and status registers which are described in detail below, as well as with six pairs of data registers (16-bit values) relating to the two input captures, the two output compares, the counter and the alternate counter. These six pairs of data registers are self-explanatory and need no further description.

TIMER CONTROL REGISTER 1 (TCR1)

Address: see Memory Map — Read/Write Reset Value: 0000 0000b

Bit 7 = ICIE

Input Capture Interrupt Enable

If ICIE is set, a timer interrupt is enabled whenever the ICF1 or ICF2 status flags of TSR are set. If the ICIE bit is cleared, the interrupt is inhibited.

Bit 6 = OCIE

Output Compare Interrupt Enable

If OCIE is set, a timer interrupt is enabled whenever the OCF1 or OCF2 status flags of TSR are set. If the OCIE bit is cleared, the interrupt is inhibited.

Bit 5 = TOIE

Timer Overflow Interrupt Enable

If TOIE is set, a timer interrupt is enable whenever the TOF status flag of TSR is set. If the TOIE bit is cleared, the interrupt is inhibited.

Bit 4 =

FOLV2

Forced Output Compare 2

When written to 1, FOLV2 forces OLVL2 to be copied to the OCMP2 pin. FOLV2 has no effect otherwise. It can only be reset by a system reset.

Bit 3 =

FOLV1

Forced Output Compare 1

When written to 1, FOLV1 forces OLVL1 to be copied to the OCMP1 pin. FOLV1 has no effect otherwise. It can only be reset by a System Reset.

Bit 2 =

OLVL2 Output Level 2

The OLVL2 bit is copied to the OCMP2 pin whenever a successful comparison occurs at OCR2.

Bit 1 =

IEDG1

Input Edge 1

The value of IEDG1 determines which type of level transition on pin ICAP1 will trigger a free running counter transfer to the ICR1. When IEDG1 is set, a rising edge triggers the capture, and when it is reset, a falling edge does.

Bit 0 = OLVL1

Output Level 1

The OLVL1 bit is copied to the OCMP1 pin whenever a successful comparison occurs at OCR1.

TIMER CONTROL REGISTER 2 (TCR2)

Address: see Memory Map — Read/Write Reset Value: 0000 0000b

Bit 7 = OC1E

Output Compare 1 Enable

If OC1E is set, the Output Compare 1 pin (OCMP1) is dedicated to the output compare 1 capability of the timer. If OC1E is reset, this pin is a general use I/O pin.

Bit 6 = OC2E

Output Compare 2 Enable

If OC2E is set, the output compare 2 pin (OCMP2) is dedicated the output compare 2 capability of the timer. If OC2E is reset, this is a general I/O pin.

Bit 5 =

OPM

One Pulse Mode

If OPM is set, the input pin ICAP1 is usable to trigger one pulse on the output pin OCMP1; the active transition on ICAP1 is given by the state of IEDG1. The length of the generated pulse depends on the the contents of OCR1.

Bit 4 = PWM

Pulse Width Modulation

If PWM is set, the output pin OCMP1 outputs a programmable cyclicsignal; the length of the pulse depends on the value of OCR1; the period depends on the value of OCR2.

Bit 3, 2 = CC1-CC0

Clock Control

00: the internal clock is divided by 4 01: the internal clock is divided by 2 10: the internal clock is divided by 8 11: the external clock is selected as shown

in the Block Diagram.

Bit 1 = IEDG2

Input Edge 2

The value of IEDG2 determines which level transition on pin ICAP2 will trigger the free running counter transfer to the ICR2. When IEDG2 is high, a rising edge triggers the capture since when low, a falling edge does.

Bit 0 = EXEDG

External Clock Edge

The status of EXEDG determines which type of level transition on the external clock pin EXCLK will trigger the free running counter. When EXEDG is set, the active transition is the rising edge; when EXEDG is reset, the active transition is the falling edge.

ICIE OCIE TOIE FOLV2 FOLV1 OLVL2 IEDG1 OLVL1

OC1E OC2E OPM PWM CC1 CC0 IEDG2 EXEDG

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16-BIT TIMER(Cont’d) TIMER STATUS REGISTER (TSR)

Address: see Memory Map — Read Only Reset Value: 0000 0000b The Timer Status Register (TSR) is an 8-bit regis-

ter of which the five most significant bits contain read-only status information and the three least significant bits are not used.

Bit 7 =

ICF1

Input Capture Flag 1

ICF1 is set when a proper edge has been sensed by the input capture edge detector at pin ICAP1. The edge is selected by the IEDG1-bit in TCR. ICF1 is cleared by a processor access to the TSR while ICF1 is set followed by an access (read or write) to the low byte of ICR1 (ICLR1).

Bit 6 = OCF1

Output Compare Flag 1

OCF1 is set when the content of the free running counter matches the content ofOCR1. It is cleared by a processor access of TSR while OCF1 is set

followed by an access (read or write) to the low byte of OCR1.

Bit 5 = TOF

Timer Overflow

TOF is set by a transition of the free running counter from FFFFh to 0000h. It is cleared by a processor access to TSR while TOF is set followed by an access (read or write) to the low byte of the counter low register. TOF is not affected by an access to the Alternate Counter Register.

Bit 4 = ICF2

Input Capture Flag 2

ICF2 is set when a proper edge has been sensed by the input capture edge detector at pin ICAP2. The edge is selected by the IEDG2-bit in TCR. ICF2 is cleared by a processor access to the TSR while ICF2 is set followed by an access (read or write) to the low byte of ICR2 (ICLR2).

Bit 3 =

OCF2

Output Compare Flag 2

OCF2 is set when the content of the free running counter matches the content of OCR2. It is cleared by a processor access of TSR while OCF2 is set followed by an access (read or write) to the low byte of OCR2.

Bit 2, 1, 0 = Unused.

ICF1 OCF1 TOF ICF2 OCF2

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4.4 SERIAL PERIPHERAL INTERFACE

4.4.1 Introduction

The Serial Peripheral Interface (SPI) allows devices to be interconnected using a minimum of wires. The SPI is synchronous and thus uses a data and a clock signal; in complex arrays, chip select lines may also be used. An SPI system may be configured as a Master and one or more Slaves, or as a system in which devices may be either Masters or Slaves. Depending on MCU specifications, one or more SPIs may be present.

4.4.2 Features

– Full duplex, three-wire synchronous transfers – Master or Slave operation – 2 MHz (maximum) Master bit frequency – 4 MHz (maximum) Slave bit frequency – Four programmable Master bit rates – Programmable clock polarity and phase – End of transmission interrupt flag – Write collision flag protection – Master mode fault protection capability.

4.4.3 Functional Description

A block diagram of the Serial Peripheral Interface (SPI) is shown inFigure 27. In a Master configuration, the Master start logic receives an input from the CPU (in the form of a write to the SPI rate generator data register) and originates the system clock (SCK) based on the internal processor clock. This clock is also used internally to control the state controller as well as the 8-bit shift register.

As a Master device, data is parallel loaded into the 8-bit shift register (from the internal bus) during a write cycle, and then shifted out serially via the MOSI pin to the Slave device(s). During a read cycle, data is received serially from a Slave device via the MISO pin and loaded into to the 8-bit shift register. When the 8-bit shift register is loaded, its data is parallel transferred to the read buffer and then made available to the internal data bus during a CPU read cycle.

In Slave configuration, the Slave start logic receives a logic low level (from a Master device) on the SS pin, and a system clock input (from the same Master device) on the SCK pin. Thus, the Slave is synchronized with the Master. Data from the Master is received serially on the Slave MOSI pin and is loaded into the 8-bit shift register.

Once the 8-bit shift register is loaded, its data is parallel transferred to the read buffer and then is made available to the internal data bus during a CPU read cycle. During a write cycle, data is parallel loaded into the 8-bit shift register from the internal data bus and then shifted out serially to the MISO pin for application to the Master device.

Figure 29 illustrates the MOSI, MISO and SCK Master-Slave interconnections. Note that the Master SS pin is tied to a logic high level and the Slave SS pin to a logic low level.

Three registers are associated with each SPI interface: the Serial Peripheral Control Register (SPCR), the Serial Peripheral Status Register (SPSR), and the Serial Peripheral Data I/O register (SPDR). These provide Control, Status, and Data functions. These registers are described in detail in the following pages.

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SERIAL PERIPHERAL INTERFACE(Cont’d) Figure 27. Serial Peripheral Interface Block Diagram

RATE

GENERATOR

MASTER

START

LOGIC

SLAVE

CONTROL

BITS

SCK

MOSI

MISO

READ

READ BUFFER

8-BIT SHIFT

WRITE

STATE

CONTROLLER

FLAGS

INTERNAL

DATA

BUS

SPCR 0Ah

SPIF

(END TX)

0Ch

(LOAD)

(FULL)

SPSR 0Bh

VR000099

LOGIC

START

CLOCK

INTERNAL

PROCESSOR

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4.4.4 Signal Description

The four basic signals (MOSI, MISO, SCK andSS) are described in the following paragraphs. Each signal function is described for both the Master and Slave mode.

The SPE (Serial Peripheral Enable) bit of the SPI Control Register enables and disables the SPI (active high); when the SPI is enabled the associated alternate functions will be attributed to the relevant I/O pins.

The SPI baud rate is the CPU clock divided by a factor defined by software (2, 4, 16, 32).

4.4.5 Master Out Slave In (MOSI)

The MOSI pin is configured as a data output in the Master (mode) device and as a data input in the Slave (mode) device.

In this manner data is transferred serially from a Master to a Slave on this line, most significant bit first, least significant bit last. The timing diagrams shown in the ELECTRICAL CHARACTERISTICS section, CONTROL TIMING subsection, illustrate SPI timing and show the relationship between data and clock (SCK).

Four possible timing relationships may be chosen by using control bits CPOL and CPHA. The Master device always allows data to be applied on the MOSI line a half-cycle before the clock edge (SCK) to allow the Slave device to latch the data.

Both the Slave device(s) and a Master device must be programmed to similar modes for proper data transfer.

When the Master device transmits data to a second (Slave) device via the MOSI line, the Slave device responds by sending data to the Master device via the MISO line. This implies full duplex transmission with both data out and data in synchronized with the same clock signal (which is provided by the Master device). Thus, the byte transmitted is replaced by the byte received and eliminates the need for separate transmit-empty and receiver-full status bits. A single status bit SPIF) is used to signify that the I/O operation is complete.

Configuration of the MOSI pin is a function of the MSTR bit in the Serial Peripheral Control Register (SPCR). When operating as a Master, the user should set the MSTR bit, defining the MOSI pin as an output

4.4.6 Master In Slave Out (MISO)

The MISO pin is configured as an input in a Master (mode) device and as an output in a Slave (mode) device. In this manner data is transferred serially from a Slave to a Master on this line, most significant bit first,least significant bit last. The MISO pin of a Slave device is placed in the high-impedance state if it is not selected by the Master, i.e. itsSS pin is at a logic high level. The timing diagram shows the relationship between data and clock (SCK). Four possible timing relationships may be chosen by using control bits CPOL and CPHA.The Master device always allows data to be applied on the MOSI line a half-cycle before the clock edge (SCK) in order for the Slave device to latch the data.

Note. The Slave device and a Master device must be programmed with similar timing modes for proper data transfer.

When the Master device transmits data to a Slave device via the MOSI line, the Slave device responds by sending data to Master device via the MISO line. This implies full duplex transmission with both data out and data in synchronized with the same clock signal (one which is provided by the Master device.) Thus, the byte transmitted is replaced by the byte received and eliminates the need for separate transmit-empty and receiver-full bits. A single status bit (SPIF) in the Serial Peripheral Status Register (SPSR) is used to signify that the I/O operation is complete.

In the Master device, the MSTR control bit in the Serial Peripheral Control Register (SPCR) should be set (by the program) to allow the Master device to receive data on its MISO pin. In the Slave device, its MISO pin is enabled by the logic high level present ontheSS pin: i.e. ifSS = 1 the MISO pin is placed in the high-impedance state, whereas ifSS = 0 the MISO pin is an output for the Slave device.

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4.4.6.1 Slave Select (SS)

The Slave select (SS) pin receives an active-low signal which is generated by the Master device, in order to enable Slave devices to accept data.

To ensure that data will be accepted by a Slave device, theSS line must be at a logic lowlevel prior to the occurence of SCK (system clock), and must remain low until after the last (eighth) SCK cycle.

Figure 28illustrates the relationship between SCK and the data for two different level combinations of CPHA, when SS is pulled low. These are :

– a) CPHA = 1 or 0, the first bit of data is applied

to the MISO line for transfer, and,

– b) when CPHA = 0 the Slave device is prevented

from writing to its data register. For further information on the effect theSS input and the CPHA have on the I/O data register, refer to the WCL status flag in the ”Serial Peripheral StatusRegister description”. A logic high level on theSS signal forces the MISO (Master In Slave Out) line to the high-impedance state. Also, SCK and the MOSI (Master Out Slave In) line are ignored by a Slave device when itsSS signal is at a logic high level.

When a device is a Master, it constantly monitors its SS signal input for the presence of a logic low level. The Master device will become a Slave device any time its SS signal input is detected as being at a logic low level. This ensures that only one Master controls theSS line.

When the SS line is detected as being at a logic low level, the Master clears the MSTR control bit (Serial Peripheral Control Register). Also, control bit SPE in the Serial Peripheral Control Register is cleared, causing the Serial Peripheral Interface

(SPI) to be disabled (SPI alternate function pins become inputs). The MODF flag bit in the Serial Peripheral Status Register is also set to indicate to the Master device that another device is attempting to become a Master. Two devices attempting to be outputs are normally the result of a software error. However, the user system can be configured in such manner as to contain a default Master which would automatically ”take-over” and restart the system.

4.4.6.2 Serial Clock (SCK)

The Serial Clock is used to synchronize the movement of data both in and out of the device via its MOSI and MISO pins. The Master and Slave devices are capable of exchanging a data byte of information during a sequence of eight clock pulses. Since the SCK is generated by the Master device, the SCK line becomes an input on all Slave devices and synchronizes Slave data transfer. The type of clock and its relationship to data are controlled by the CPOL and CPHA bits in the Serial Peripheral Control Register.

The Master device generates the SCK through a circuit driven by the internal processor clock. Two bits (SPR0 and SPR1) in the Serial Peripheral Control Register of the Master device select the clock rate. The Master device uses the SCK to latch incoming Slave device data on the MISO line and shifts out data to the Slave device on the MOSI line. Both Master and Slave devices must be operated in the same timing mode as defined by the CPOL and CPHA bits in the Serial Peripheral Control Register.

In the Slave device, SPR0 and SPR1 have no effect on the operation of the Serial Peripheral Interface.

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SERIAL PERIPHERAL INTERFACE(Cont’d) Figure 28.Data Clock Timing Diagram

Figure 29. Serial Peripheral Interface Master Slave

SCK

MISO/MOSI

(CPOL=0, CPHA=0)

(CPOL=0, CPHA=1)

(CPOL=1, CPHA=0)

(CPOL=1, CPHA=1)

MSB

LSB654

INTERNAL STROBE FOR DATA CAPTURE (ALL MODES)

SCK

VR000098

8-BIT SHIFT REGISTER

MASTER

SLAVE

SPI

MISO

MOSI

SCK

+5V

8-BIT SHIFT REGISTER

CLOCK

GENERATOR

MISO

MOSI

SCK

VR000100

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4.4.7 Serial Peripheral Control Register (SPCR)

Address: see Memory Map — Read/Write Reset Value: 0Xh

The Serial Peripheral Control Register bits are defined as follows.

Bit-7 = SPIE

Serial Peripheral Interrupt Enable

When the Serial Peripheral Interrupts Enable bit is set a processor interrupt can occur. This forcesthe proper vector to be loaded into the program counter if the Serial Peripheral Status Register flag bit (SPIF) and /or MODF are set. SPIE does not inhibit the setting ofa status bit. The SPIE bit is cleared on Reset.

Bit-6 = SPE

Serial Peripheral output Enalble

When the Serial Peripheral Output Enable Control bit is set, all output drive is applied to the external pins and the system is enabled. When the SPE bit is set, it enables the SPI system by connecting it to the external pins thus allowing it to interface with the external SPI bus. The pins that are defined as outputs depend on which mode (Master or Slave) the device is in. Because the SPE bit is cleared on Reset, the SPI system is not connected to the external pins on Reset.

Bit-4 =

MSTR

Master

The Master bit determines whether the device is a Master or a Slave. If the MSTR bit is reset it indicates a Slave device, whent it is set it indicates a Master device. If the Master mode is selected, the function of the SCK pin changes from an input to an output and the function of the MISO and MOSI pins are reversed. This allows the user to wire device pins MISO to MOSI, and MOSI to MOSI, and SCK to SCK without incident. The MSTR bit is cleared on Reset: thus the device is always set in Slave mode during Reset.

Bit-3 =CPOL

Clock POLarity

The Clock POLarity bit controls the normal or steady state value of the clock when no data is being transferred. The CPOL bit affects both the Master and Slave modes. It must be used in conjunction with the Clock PHAse control bit (CPHA) to produce the wanted clock-data relationship between a Master and a Slave device. When the CP0L bit is reset, it produces a steady-state logic low value on the SCK pin of the Master device. If the CPOL bit is set, a logic high level is present on the SCK pin of the Master device when data is not being transferred. The CPOL bit is not affected by Reset.

Bit-2 =

CPHA

Clock PHAse

The Clock PHAse bit controls the relationship between the data on the MISO and MOSI pins and the clock produced or received at the SCK pin. This control has effect in both the Master or Slave modes. It must be used in conjunction with the Clock Polarity control bit (CPOL) to produce the wanted clock-data relationship. In general the CPHA bit selects the clock edge which captures data and allows it to change states. It has its greatest impact on the first bit transmitted (MSB) in that it does or does not allow a clock transition before the first data capture edge. The CPHA bit is not affected by Reset.

Bit-1 =SPR1

Serial Peripheral Rate bit 1

Bit-0 =

SPR0

Serial Peripheral Rate bit 0

These two Serial Peripheral Rate bits select one of four baud rates to be used for SCK when the device is a Master. However, these two bits have no effect in Slave mode. The Slave device is capable of shiftingdata in and out at a maximum rate which is equal to the CPU clock. A rate table is given below for SCK inMaster mode. The SPR1 and SPR0 bits are not affected by Reset.

SPIE SPE - MSTR CPOL CPHA SPR1 SPR0

SPR1 SPR0

Internal Processor

Clock Division factor

00 2 01 4 10 16 11 32

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4.4.8 Serial Peripheral Status Register (SPSR)

Address: see Memory Map — Read Only Reset Value: 00h

The status flags which generate a Serial Peripheral Interface (SPI) interrupt may be blocked by the SPIE control bit in the Serial Peripheral Control Register. The WCOL bit does not cause an interrupt. The Serial Peripheral Status register bits are defined as follows:

Bit-7 =

SPIF

Serial Peripheral Data Transfer Flag

The Serial Peripheral Data Transfer Flag bit notifies the user that a data transfer between the device and an external device has been completed. With the completion of the data transfer, SPIF is set, and if SPIE is set, a Serial Peripheral Interrupt is generated. During the clock cycle SPIF is being set, a copy of the received data byte in the shift register is moved to a buffer. When the data register is read, it is the buffer that is read. In the event of an overrun condition, when the Master device has sent several bytes of data and the Slave device has not responded to the first SPIF, only the first byte sent is contained in the receive buffer, and all other bytes are lost.

Data transfer is initiated by the Master device writing to its Serial Peripheral Data I/O Register.

Clearing the SPIF bit is accomplished by a software sequence which accesses the Serial Peripheral Status Register while SPIF is set, followed by a write or read operation on the Serial Peripheral Data I/O Register.

In the Master device, while SPIF isset, all writes to the Serial Peripheral Data I/O Register are inhibited until the Serial Peripheral Status Register is read.

In the Slave device, SPIF can be cleared (using a similar sequence) during a second transmission; however, it must be cleared before the second SPIF bit in order to prevent an overrun condition. The SPIF bit is cleared on Reset.

Bit-6 = WCOL

Write Collision status bit

The Write Collision Status bit informs the user that an attempt was made to write to the Serial Peripheral Data I/O Register while a data transfer was taking place with an external device. The transfer

continues uninterrupted, and therefore a write will be unsuccessful. A ”read collision” cannot occur, since the received data byte is placed in a buffer in which access is always synchronous with the MCU operation. If a ”write collision” occurs, WCOL is set but no SPI interrupt is generated. The WCOL bit is a status flag only.

Clearing the WCOL bit is accomplished by a software sequence of accessing the Serial Peripheral Status Register while WCOL is set, followed by:

1) A read of the Serial Peripheral Data I/O Register prior to the SPIF bit being set, or

2) A read or write of the Serial Peripheral Data I/O Register after the SPIF bit is set.

A write to the Serial Peripheral Data I/O Register (SPDR) prior to the SPIF bit being set, will result in generation of another WCOL status flag. Both the SPIF and WCOL bits will be cleared in the same sequence. If a second transfer has started while trying to clear the (previously set) SPIF and WCOL bits with a clearing sequence comprising a write to the Serial Peripheral Data I/O Register, only the SPIF bit will be cleared.

A collision of a write to the Serial Peripheral Data I/O Register while an external data transfer is taking place can occur both in the Master mode and the Slave mode, although with proper programming the Master device should have sufficient information to preclude this collision.

Collision in the Master device is defined as a write of the Serial Peripheral Data I/O Register while the internal rate clock (SCK) is in the process of transfer. The signal on theSS pin is always at a logic high level on the Master device.

Collision in a Slave device is defined in two separate modes. A problem arises in a Slave device when the CPHA control bit is reset. When CPHA is reset, data is latched on the occurence of the first clock transition. The Slave device does not have any way of knowing when that transition will occur; therefore, the Slave device collision occurs when it attempts to write the Serial Peripheral Data I/O Register after itsSS pin has been pulled low. If the CPHA bit is reset, theSS pin on the Slave device freezes the data in its Serial Peripheral Data I/O Register and does not allow it to be altered.

The Master device must raise the SS pin of the Slave device to a logic high level between each byte it transfers to the Slave device

SPIF WCOL - MODF - - - -

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The second collision mode is defined by the CPHA control bit being set. With the CPHA bit set, the Slave device will be receiving a clock (SCK) edge prior to the latch of the first data transfer. This first clock edge will freeze the data in the Slave device I/O register and allow the msb on to the external MISO pin of the Slave device. A logic low state on the SS pin enables the Slave device, however, data is not output on the MISO pin until the first edge of the data transfer clock. The WCOL bit will only be set if the I/O register is accessed while a transfer is taking place. In this second collision mode, a Master device can hold a Slave device’s SS pin low during the transfer of several bytes of data without this causing any problems.

Unlike other SPI interfaces, there is no special case of collision which remains undetected by the WCOL bits. The WCOL bit is TOTALLY reliable with regard to collision detection.

Since theSlave deviceis operating asynchronously with the Master device, the WCOL bit may be used as an indicator of a collision occurence. This helps alleviate the user from a strict real-time programming effort. The WCOL is cleared on Reset.

Bit-4 = MODF

Mode Fault flag

The function of the mode fault flag is defined for the Master mode (device). If the device is a Slave device the MODF bit will be prevented from toggling from reset to set; however, this does not prevent the device from being in the Slave mode with the MODF bit set.

The MODF bit is normally reset, and is set only when the Master device has itsSS pin pulled low. Toggling the MODF bit to the set state affects the internal Serial Peripheral Interface (SPI) system in the following ways:

a) MODF is set and SPI interrupt is generated if SPIE is set.

b) The SPE bit is forced to a reset state. This blocks all output from the device and disables the SPI system.

c) The MSTR bit is forced to a reset state, thus forcing the device into the Slave mode.

Clearing the MODF is accomplished by a software sequence which accesses the Serial Peripheral Status Register while MODF is set, followed by a write to the Serial Peripheral Control Register.

To avoid multiple Slave conflicts in a system comprising several MCUs, the SS pin must be pulled high during the clearing sequence of MODF. Control bits SPE and MSTR may be restored to their original set state during this clearing sequence, or after the MODF bit has been cleared. Hardware does not allow the user to set the SPE and MSTR bits while MODF is set, unless this occurs during the proper clearing sequence. The MODF flag bit indicates the possible occurrence of a Multimaster conflict for system control, and allows proper exit from normal system operation to Reset or to a default system state. The MODF bit is cleared on Reset.

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ST7285C

SERIAL PERIPHERAL INTERFACE(Cont’d)

4.4.9Serial Peripheral Data I/O Register (SPDR)

Address: see Memory Map — Read/Write Reset Value: XXh

The Serial Peripheral Data I/O Register is used to transmit and receive data on the serial bus. Only a write to this register will initiate transmission/reception of another byte and this will only occur in the Master device. A Slave device writing to its data I/O register will not initiate a transmission. After having transmitted a byte of data, theSPIF status bit is setin both the Master and Slave devices.

A write or read of the Serial Peripheral Data I/O Register, after accessing the Serial Peripheral Status Register with SPIF set, will clear SPIF.

During the clock cycle the SPIF bit is being set, a copy of the received data byte in the shift register is being moved to a buffer. When the user reads the Serial Peripheral Data I/O Register, the buffer is actually being read. During an overrun condition, when the Master device has sent several bytes of data and the Slave device has not internally responded to clear the first SPIF, only the first byte is contained in the receive buffer of the Slave device; all others are lost. The user may read the buffer at any time. The first SPIF must be cleared by the time a second transfer of data from the shift register to the read buffer is initiated, otherwise an overrun condition will exist.

A write to the Serial Peripheral Data I/O Register is not buffered, and data is placed directly in the shift register for transmission.

The ability to access the Serial Peripheral Data I/O Register is limited when a transmission is taking place. Please refer to the description of the WCOL and SPIF status bits inorder to fully appreciate the rules governing the use of the Serial Peripheral Data I/O Register.

4.4.10 Single Master And Multimaster Configurations

There are two types of SPI systems, single Master and Multimaster.

A typical Single Master system may be configured, using one MCU as the Master and four others as Slaves. The MOSI, MISO and SCK pins are all wired to equivalent pins on each device. The Master device generates the SCK clock, whereas the Slave devices all receive it. Since the MCU Master device is the bus Master, it internally controls the function of its MOSI and MISO lines, thus writing data to the Slave devices on the MOSI and reading data from the Slave devices on the MISO lines.

The Master device selects the individual Slave devices by using four pins of a parallel port to control the four SS pins of the Slave devices. A Slave device is selected when the Master device pulls its SS pin low. The SS pins are pulled high, thus disabling the Slave devices during Reset, since the Master device ports will be forced as inputs.

Note that Slave devices need not be enabled in a mutually exclusive fashion, except in order to prevent bus contention on the MISO lines. An example of this is a write to several display drivers to clear a display using a single I/O operation.

To ensure that proper data transmission takes place between the Master device and a Slave device, the Master device may ask the Slave device to respond by echoing a previously received data byte (this data byte can be inverted, or at least be different from the last one sent by the Master device). The Master device will always receive the previous byte back from the Slave if all MISO and MOSI lines are connected and the Slave has not written its data I/O register. Other transmission security methods may be defined using ports as handshake lines, or by means of data bytes containing command fields.

A Multimaster system may also be configured by the user. An exchange of Master control can be implemented by adopting a handshake scheme using the I/O ports, or by an exchange of code messages via the Serial Peripheral Interface system. The principal device controls are the MSTR bit in the Serial Peripheral Control Register and the MODF bit in the Serial Peripheral Status Register.

XXXXXXXX

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4.5 I2C BUS INTERFACE

4.5.1 Introduction

The I2C Bus Interface serves as an interface between the MCU and the serial I2C bus. It provides both multimaster and multislave functions, and controls all I2C bus-specific sequencing, protocol, arbitration and timing.

4.5.2 General Features

– Parallel bus/I2C protocol converter – Multi-Master capability – Interrupt generation – Standard I2C mode/Fast I2Cmode – 7-bit Addressing/10-bit Addressing

4.5.2.1 I2C Master Mode Features:

– Flag indicating when the I2C bus is in use – Flag indicating the loss of arbitration – Flag indicating the end of the byte transmission – Transmitter/Receiver flag – Clock generation

4.5.2.2 I2C Slave Mode Features:

– Start bit detection flag – Detection of a misplaced Start or Stop condition – Detection of a problem during transfer – Address Matched detection – General call detection – Flag indicating the end of the byte transmission – Transmitter/Receiver flag

4.5.3 Functional Description

In addition to receiving and transmitting data, this interface converts it from serial to parallel format and vice versa, using either an interrupt or polled handshake. The interrupts are enabled or disabled by software. The interface is connected to the I2C bus by a data pin (SDA) and by a clock pin (SCL). It can be connected both with a standard I2C bus and a Fast I2C bus. This selection is made by software.

The interface can operate in the four following modes:

– Master transmitter – Master receiver – Slave transmitter – Slave receiver When it is inactive, it operates in Slave Mode.

This interface enables the multimaster function thanks to an automatic switch between Master and Slave mode in the event of a loss of arbitration:

the Slave process is always active when a start condition is detected on the SDA line. When acting as Master, it initiates a data transfer and generates the clock signal. A serial data transfer always begins with a start condition and ends with a stop condition. Both start and stop conditions are software generated in Master mode. In Slave mode, the interface is capable of recognising its own address (7-bit or 10-bit), a general call address or a start byte. The general call may be enabled or disabled by software.

Data and addresses are transferred as 8-bit bytes, MSB first. The first byte following the start condition in 7-bit addressing (two first bytes in 10-bit addressing) is the address byte; it is always transmitted in Master mode. A 9th clock pulse follows the 8 clock cycles of a byte transfer, during which the receiver must send an acknowledge bit to the transmitter. Acknowledge may be enabled and disabled by software.

When in Transmitter mode, the interface waits for the MCU to write the byte in the Data Register, by holding the clock line low before transmission; when in Receiver mode, it waits for the MCU to read the byte in the Data Register by holding the clock line low after reception.

The I2C Bus Interface has seven internal registers. Three of these are used for interface initialization (Own Address Registers and Clock Control Register). The remaining four registers are used during data transmission/reception (Data Register, Control Register and Status Register).

The SCL frequency (F

scl

) is controlled by a programmable clock divider which depends on the I2C bus mode. The I2C interface address is stored in two registers (OAR) in order to allow 10-bit addressing.

The Peripheral Enable bit (bit 6) of the I2C Control Register activates the I2C interface and configures the I/O as I2C pins. The speed of the I2C interface may be selected between 100KHz and 400KHz.

When the I2C cell is enabled, PA4 and PA6 are configured as open-drain. Inthis case, the external pull-up resistance should be 10KΩ or more.

When the I2C cell is disabled, PA4 and PA6 revert to being standard I/O port pins.

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ST7285C

I2C BUS INTERFACE (Cont’d) Figure 30. I2C Interface Block Diagram

DATA REGISTER

DATA SHIFT REGISTER

COMPARATOR

OWN ADDRESS REGISTER

CLOCK CONTROL REGISTER

STATUS REGISTER 1

CONTROL REGISTER

CONTROL

DATA

CLOCK

CONTROL

SDA

SCL

LOGIC

DDC2B ADDRESS

STATUS REGISTER 2

Vsync

IT BUFF

DMAACK

DMA

DATA BUS

CONTROL SIGNALS

INTERRUPT

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ST7285C

I2C BUS INTERFACE (Cont’d)

4.5.4 EPROM/ROM I C COMPATIBILITY APPLICATION NOTE

In order to insure full compatibility between the EPROM and the ROM v ersions of the ST7285 microcontroller, cer tain timing conditions have to be respected when using the I2C interface.

Otherwise the I2C interface of t he ST72E85 ca n: – Detect an unexp ected START or STOP condi-

tion with BUS ERROR detec tion

– Generate unexpected B TF flag settings

Unexpected START or STOP condition detection

In the ST72E85 device, due to the syn chronisation between the I2C peripheral and the f

CPU

(4.332MHz), an unexpected START or STOP condition can be detected in S lave mode. This generates an unexpected Bus Error and s ets the BERR bit in the SR2 register.

To avoid this effect, t he following I C timing has to be respected:

–tsu

DAT

>1/f

CPU

~ 230,84ns

–thd

DAT

>1/f

CPU

~ 230,84ns

In the ROM version of the ST7285, the I2C peripheral and F

CPU

are asynchronous, so n o unexpect-

ed START or STOP conditi on can be detected.

Unexpected BTF flag setting after a STOP condition

Due to the reason described in the previous paragraph, the BTF flag can be se t unexpectedly in the I2C interface of the ST72E85 after a STOP condition is detected in Slave mode.

To recover from this condition, res et and subsequently set the PE bit in the CR register when the STOPF a nd BTF flag s are set at the same time after a STOP c ondition detection.

The I2C interface is not su bject to this effect in the ROM version of the S T7285.

Figure 31. I C Ti ming Diagram

SDA

SCL

tsu

DAT

thd

DAT

DATA bitSTART b it

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I2C BUS INTERFACE (Cont’d)

4.5.5 Register Description CLOCK CONTROL REGISTER (CCR)

Address: 002Bh — Read / Write Reset Value: 00h

b7:

FM/SM

Fast / Standard I2Cmode

When the bit is set to 1 the interface operates in the fast I2C bus mode.

When the bit is set to 0 the interface operates in the standard I2C bus mode.

b6-0: D6-D0

7 bit divider programming

Implementation of a programmable clock divider In Standard I2C mode:

Fscl = PHI1/(2x([D6..D0]+2)); in this case, Fscl varies between 15.75KHz and 100 KHz (if PHI1=4MHz). In Fast I2C mode: Fscl = PHI1/(3x([D6..D0]+2)); in this case, Fscl varies between 10.5 KHz and 333KHz (if PHI1=4MHz).

Table 8. Example of SCL frequency with PHI1 = 4 MHz in Standard I2C mode

FM/SM CC6 CC5 CC4 CC3 CC2 CC1 CC0

FM/SM D6 D5 D4 D3 D2 D1 D0 Fscl(Khz)

0 0010010 100 0 0011011 70 0 0100110 50 0 1001110 25 0 1111111 15.75 1 0000010 333 1 0000101 190 1 0000110 167 1 0001101 89 1 0011011 43 1 1111111 10.5

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I2C BUS INTERFACE (Cont’d) DATA REGISTER (DR)

Address: 002Eh — Read / Write Reset Value: 00h

In transmitter mode, DR contains the next byte of data which is to be applied to the shift register. The byte transmission begins after the DR write by the microcontroller.

In receiver mode, DR contains the last byteof data received from the shift register. The next byte receipt begins after the DR read by the microcontroller.

OWN ADDRESS REGISTER 1 (OAR1)

Address: 002Ch — Read / Write Reset Value: 00h

In 7-bit addressing, [ADD7..ADD1] are the address of the peripheral.

In 10-bit addressing, [ADD7..ADD0] are the least significant bits of the address of the peripheral.

OWN ADDRESS REGISTER 2 (OAR2)

Address: 002Dh — Read / Write Reset Value: 00h

b7-3 = reserved. b2-1 = [ADDE2..ADDE1] are the most significant

bits of the address of the peripheral in 10-bit addressing.

In 7-bit addressing, the first byte following the start condition is the address byte. The least significant bit is the data direction bit.

In 10-bit addressing, the first two bytes following a start condition are the address bytes. The first seven bits of the first byte are the combination 11110xx of which the last two bits are the two most significant bits of the 10-bits addressing; the eighth bit is the data direction bit. The second byte contains the remaining 8 bits of the 10-bit address.

b0 = reserved. Various combinations of read/write formats in 10-

bit addressing:

Master-transmitter/Slave-receiver

When a 10-bit address follows a start condition (S), each Slave compares the first seven bits of the first byte of the Slave address (11110xx) with its own address and tests the eighth bit. If the Slave finds a match, it generates an acknowledge (A1) and it compares the eight bits of the second byte (xxxxxxxx) with its own address. If the Slave finds a match, it generates an acknowledge (A2). The Slave will remain addressed until it receives a stop condition or a repeated start condition followed by a different Slave address.

Master-receiver/Slave-transmitter

The direction of the transfer is changed after the second data direction bit. Up to the acknowledge bit A2, the procedure is the same as the one described for a Master-transmitter/Slave-receiver. After a repeated start condition, the Slave remembers that it was addressed before. Then it compares the seven bits of the first byte (11110XX) with its own address.

DR7 DR6 DR5 DR4 DR3 DR2 DR1 DR0

ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 ADD0

-----ADDE2ADDE1-

Slave_address

1st 7bits

0A1

Slave_Adress

2nd byte

A2 data A

Slave_adress

1st 7bits

0A1

Slave_Adress

2nd byte

A2 data

Slave_adress

1st 7bits

1 A data A

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ST7285C

I2C BUS INTERFACE (Cont’d) CONTROL REGISTER (CR)

Address: 0028h — Read / Write Reset Value: 00h

b7-6 = reserved. b5: PE

Peripheral Enable

1 : Master/Slave capability. 0 : Peripheral disabled ( all outputs are released). When this bit is reset, all the bits of the control register and the status register except the Stop bit are reset. PE selects the alternate function on the corresponding I/O. This bit is set by software and it is cleared by software or by a reset.

b4: ENGC

Enable General call

When this bit is set, the peripheral acknowledges the general call address. Engc bit is set or cleared by software. It is cleared when the peripheral is disabled (PE=0) or by reset.

b3: START

Generation of a Start condition

When the Start bit is set in Slave mode, the interface generates a Start condition as soon as the bus is free. In Master mode, it generates a repeated Start condition. Then an interrupt is generated if ITE is set. This bit is set by software and is cleared by software, when the peripheral is disabled (PE=0) or by reset. It is automatically cleared after the start condition is sent.

b2: ACK

Acknowledge level

When this bit is set, an acknowledge is returned after an address byte is received or after a data byte is received. When it is cleared, no acknowledge is returned. It is set by software and it is cleared by software, when the peripheral is disabled (PE=0) or byreset.

b1: STOP

Generation of a Stop condition

If the Stop bit is set in Master mode then a stop condition is generated after the transfer of the current byte or after that the current Start condition is sent. If it is set in Slave mode then both SCL and SDA lines are released in order to recover from an error condition and the peripheral waits for a detection of a Start or a Stop condition. Then the interface waits for a Stop or a Start condition on the lines. This bit can be cleared by software. It is automatically cleared after the stop condition is sent on the SCL line in Master mode or by reset.

b0: ITE

Interrupt Enable

When the Interrupt Enable bit is set, the I2C interface interrupt is generated after anyone of these following conditions

– A Start condition is generated in Master mode. – The address is matched in Slave mode while the

ACK flag is at a logic high.

– A data byte has been received or is to be trans-

mitted.

– A loss of arbitration of the bus to another Master

in Master mode. – A misplaced Start or Stop condition is detected – There is no acknowledge. – A Stop condition has been detected in Slave

mode. While the ITE flag is set, an interrupt is

generated, SCL is hold low and the transfer is

suspended except when a loss of arbitration or a

detection of a Stop condition have been detect-

ed. ITEis reset by software, when the peripheral

is disabled (PE=0) or by reset.

- - PE ENGC START ACK STOP ITE

PE = 0 PE = 1 PA6 = normal I/O PA6 = I

C DATA

PA4 = normal I/O PA4 = I

C CLOCK

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ST7285C

I2C BUS INTERFACE (Cont’d) STATUS REGISTER 1 (SR1)

Address: 0029h — Read Only Reset Value: 00h

b7:

SR2F

Status Register 2 Flag

SR2F is set when at least one flag in the Status Register 2 is set. It is cleared when all these flags are reset.

b6:

ADD10

10 bit Master Addressing Mode

ADD10 is set when the 10 bit addressing mode header (”11110xxx”) is sent as the first address byte. When this bit is set, an interrupt is sent to the microcontroller if ITE is set This bit is cleared by a read of the Status Register, followed by a write in the Data Register. It is also cleared when the peripheral is disabled (PE=0) or by reset.

b5: TRA

Transmitter/Receiver

TRA is set when the interface is in data transmission mode.

It is cleared by the detection of a stop condition, by a loss of the bus arbitration (ARLO set). It is also cleared when the peripheral is disabled (PE=0) or by reset.

b4: BUSY

Bus Busy

BUSY bit is active when there is a communication in progress on line. The detection of the communications is always active (even if the peripheral s disabled). This bit is set by the detection of a Start condition and it is cleared by the detection of a Stop condition or by reset.

b3: BTF

Byte Transfer Finished

- In transmitter mode, BTF bit is set after the transmission of a data byte and an acknowledge clock pulse. It is cleared by a read of the Status Register (with BTF set), followed by a write in the Data Register.

In receiver mode, BTF bit is set after the reception of the acknowledge of a byte. It is cleared by a reading of the Status Register (with BTF set), followed by a read of the Data Register.

It is also cleared when the peripheral is disabled (PE=0) or by reset.

When BTF is set, the I2C interrupt occurs if ITE is set. Then the microcontroller must access the data register.

b2:

ADSL

Addressed as Slave

ADSL bit is set when the address comparator recognizes either its own Slave address or the general call address. When this bit is set , an interrupt is sent to the microcontroller if ITE is set. This bit is cleared by a read of the status register (when ADSL is set). Itis also cleared when the peripheral is disabled (PE=0) or by reset.

b1:

M/SL

Master/Slave

M/SL bit is set when the interface generates a Start condition. When it is set, the interface operates in Master mode. It is cleared by the detection of a Stop condition, by a loss of arbitration, by reset or when the peripheral is disabled (PE=0).

b0: SB

Start Bit ( in Master mode)

In Master mode , SB bit is set when the hardware has generated a Start condition. When this bit is set, an interrupt is sent to the microcontroller if ITE is set. Then the microcontroller must write the address byte in the data register. This bit is cleared by a read of the status register (when SB is set), followed by a write in the data register. It is also cleared when the peripheral is disabled (PE=0) or by reset.

SR2F ADD10 TRA BUSY BTF ADSL M/SL SB

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ST7285C

I2C BUS INTERFACE (Cont’d) STATUS REGISTER 2 (SR2)

Address: 002Ah — Read Only Reset Value: 00h

b7-5 = reserved. b4: AF

Acknowledge Failure

The Acknowledge Failure bit is set when no acknowledge is returned. If this bit is set, then an interrupt is sent to the microcontroller if ITE is set. During this interrupt, the SCL line is not hold low. This bit is cleared by a read of the Status Register. It is also cleared when the peripheral is disabled (PE=0) or by reset.

b3: STOPF

Stop Detection Flag (in Slave mode)

StopF bit is set when a Stop condition is detected on the SCL line after an acknowledge of byte. When this bit is set, an interrupt is sent to the microcontroller if ITE is set. During this interrupt, the SCL line is not hold low. This bit is cleared by a read of the status register (when StopF is set). Itis also cleared when the peripheral is disabled (PE=0) or by reset.

b2:

ARLO

Arbitration Lost

ARLO is set when the I2C interface loses the arbitration of the bus to another Master. After ARLO is set, the interface operates in Slave mode (M/SL at a logic low) and an interrupt is generated if ITE is set. During this interrupt, the SCL line is not hold low. This bit is cleared by a read of the Status register. It is also cleared when the peripheral is disabled (PE=0) or by reset.

b1: BERR

Bus Error

BERR bit is set when a misplaced start or stop condition is detected. If this bit is set, then an interrupt is sent to the microcontroller if ITE is set. During this interrupt, the SCL line is not hold low. The Bus Error flag bit is cleared by a read of the status register (when BERR is set). It is also cleared when the peripheral is disabled (PE=0) or by reset.

b0: GCAL

General Call (Slave mode)

If ENGC is set, GCAL is set following detection of a general call address.

It is cleared by the detection of a stop condition, by reset or when the peripheral is disabled (PE=0).

4.5.6 I2C State Machine:

In I2C mode, the I2C interface always operates in Slave mode (M/SL at logic low level) except when it initiates a transmission or a receive sequence.

It enables the multimaster function with an automatic switch from Master mode to Slave mode when the interface loses the arbitration of the I2C bus. So, the Slave process is active both in Slave mode and in Master mode.

4.5.6.1 Slave mode

As soon as a start condition is detected, the address word is received from the SDA line and it is sent to the shift register; then it is compared with the interface address.

– Address no matched: the state machine is reset

and it waits for another Start bit.

– Address matched: the Addressed As Slave bit

(ADSL) is set and an acknowledge bit is sent to the Master if ACK is set. So an interrupt is sent to the microcontroller if ITE is set; it then waits for the microcontroller to read Status Register 1 by holding the SCL line low.

Then, depending on the Data Direction bit (least significant bit), and after generating an acknowledge, the Slave must enter Send or Receive mode.

4.5.6.2 Slave Receiving

The Slave receives words from the SDA line into the shift register and it sends them to the data register. After each word it generates an acknowledge bit if the Enable Acknowledge flag is set. When the acknowledge bit is sent, the BTF flag is set and an interrupt is generated if ITE is set.Then it waits for the microcontroller to read the Data Register by holding the SCL line low.

- Detection of a Stop or a Start condition during a byte reception: the BERR flag is set and an interrupt is generated.

- Detection of a Start condition after an acknowledge time-slot: the state machine is reset and starts a new process.

- Detection of a Stop condition after an acknowledge time-slot: the Slave state machine is reset. Then the SSTOP flag is set and an interrupt is generated if ITE is set.

- The Stop bit is set in the control register: the state machine is reset after transfer of the current byte.

- - - AF STOPF ARLO BERR GCAL

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ST7285C

I2C BUS INTERFACE (Cont’d)

4.5.6.3 Slave Sending

The Slave waits for the microcontroller to write in the Data Register. Then it receives data in the Shift Register and sends it on the SDA line. When the acknowledge bit is received, the BTF flag is set and an interrupt is generated if ITE is set.

- Detection of a Stop or Start condition during a byte transfer: the state machine is reset, the BERR flag is set and an interrupt is generated.

- Detection of a Start condition after an acknowledge time-slot: the state machine is reset and it starts a new process. So, the flag ADSL is set and an interrupt is generated if ITE is set.

- Detection of a Stop condition after an acknowledge time-slot: the state machine is reset. Then the flag SSTOP is set and an interrupt is generated if ITE is set.

4.5.6.4 Master mode

The interface operates in Master mode after generating a Start condition. So, the Start flag must be set in the control register and the I2C bus must be free (Busy bit at logic low level). Once the Start condition is generated, the M/SL and SB flags are set and an interrupt is generated if ITE is set. The interface waits for the microcontroller to write the Slave address in the Data Register by holding the SCL line low. The address byte is then sent on the SDA line, an acknowledge clock pulse is sent on the SCL line and an interrupt is generated if ITE is set. The interface waits for the MCU to write to the Control Register by holding the SCL line low. If there is no acknowledge, the AF flag is set and the Master must write a Start or a Stop in the Control Register.

The state machine then enters a send or a receive process, depending on the state of the Data Direction bit (least significant bit); an interrupt is generated if ITE is set.

If the Master loses control of bus arbitration, there will be no acknowledge. The AF flag is set and the Master must write a Start or a Stop in the control register; the ARLO flag is set, the M/SL flag is cleared and the process is reset. An interrupt is generated if ITE is set.

4.5.6.5 Master Sending

The Master waits for the MCU to write in the Data Register by holding the SCL line low. Then the byte is received in the shift register and is sent on the SDA line. The BTF flag is set and an interrupt is generated if ITE is set.

- Detection of a Stop or of a Start condition during a byte transfer: the BERR flag is set and an interrupt is generated if ITE is set.

- The Stop bit is set in the Control Register: a Stop condition is generated after the transfer of the current byte, the M/SL flag is cleared and the state machine is reset. Then an interrupt is generated if ITE is set.

- The Start bit is set in the Control Register: the state machine is reset and it starts a new process. The SB flag is set and an interrupt is generated if ITE is set.

- There is no acknowledge: the AF flag is set and an interrupt is generated if ITE is set.

4.5.6.6 Master Receiving

The Master receives a byte from the SDA line into the shift register and it sends it to the Data Register. So, it generates an acknowledge bit if the ACK bit is set and it generates an interrupt if ITE is set. Then it waits for the microcontroller to read the Data Register by holding SCL line low.

- A detection of a Stop or a Start condition during a byte reception: the flag BERR is set and an interrupt is generated if ITE is set.

- The Start bit is set in the Control Register: the state machine is reset and starts a new process. So, the flag SB is set and an interrupt is generated if ITE is set.

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ST7285C

I2C BUS INTERFACE (Cont’d) Transfer sequencing:

Master transmitter: (M/SL=1)

IT1: SB =1. This interrupt is cleared by a read of SR1 followed by a write in DR. IT2: This interrupt is cleared by a read of SR1 followed by a write in CR and in DR. IT3: BTF=1; TRA=1. This interrupt is cleared by a read of SR1 followed by a write in DR.

Master receiver: (M/SL=1)IT4: This interrupt is cleared by a read of SR1 followed by a write in CR.

IT5: BTF=1. This interrupt is cleared by a read of SR1 followed by a read of DR. Slave transmitter: (M/SL=0)

IT6: ADSL =1. This interrupt is cleared by a read of SR1 followed by a write in DR. IT7: BTF=1, TRA=1. This interrupt is cleared by a read of SR1 followed by a write in DR. IT8: StopF=1. This interrupt is cleared by a read of SR2.

Slave receiver: (M/SL=0)

IT9: ADSL =1. This interrupt is cleared by a read of SR1. IT10: BTF=1. This interrupt is cleared by a read of SR1 followed by a read of DR.

10 bits addressing (Master): Master:

IT11: ADD10=1. This interrupt is cleared by a read of SR1 followed by a write in DR. Slave:

During IT1,2,3,4,5,6,7,9,10,11 the SCL line is hold low. S: Start; P: Stop; A: Acknowledge; IT: interrupt.

Detailed timing information is available in the ELECTRICAL CHARACTERISTICS.

S IT1 ADD A IT2 IT3 DATA A IT3 DATA A IT3 P

S IT1 ADD A IT4 DATA A IT5 DATA A IT5 P

S ADD A IT6 IT7 DATA A IT7 DATA A IT7 P IT8

S ADD A IT9 DATA A IT10 DATA A IT10 P IT8

S ADD A IT11 ADD A IT2

S ADD A ADD A

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4.6 A/D CONVERTER (ADC)

4.6.1 Introduction

The on-chip Analog to Digital Converter peripheral is a single 8-bit successive approximation ratiometric monotonic ADC, to which up to 8 different analog voltages (depending on device specification as illustrated in Block Diagram) may be applied from external sources. The result of the conversion is stored in the 8-bit Data Register. The A/ D converter is controlled through the ADC Control/ Status Register.

4.6.2 Functional Description

The A/D converter is enabled by setting the A/D Converter ON bit (ADON) in the ADC Control/Status Register. A delay time is then required for the converter to stabilize (typically 10µs, see Electrical Characteristics)).

When the A/D function is enabled, the associated pins (see MCU Block Diagram) may be used as analog inputs. The inputs must first be enabled for analog input by setting the corresponding bit(s) of the relevant Port Configuration Register as described in the Section on I/O Ports. Bits CH2 to CH0 of the A/D Converter Control/Status Register may then be coded to select the channel to be converted. Using a pin, or pins, as analog inputs does not affect the ability to read the port as logic inputs.

The A/D converter may be disabled by resetting the ADON bit. This feature allows the reduction of power consumption when no conversion is in progress. The A/D converter is disabled after Power-On and external resets.

When enabled, the A/D converter performs a continuous conversion of the selected channel. When

a conversion is completed (16 µs for f

CPU

=4 MHz), the result is loaded into the read only Result Data Register and the COCO (Conversion Complete) flag is set. No interrupt is generated. Any write to the A/D Converter Control/Status Register aborts the current conversion, resets the COCO flag and starts a new conversion.

The A/D converter is ratiometric. An input voltage equal to, or greater than V

DD ,

converts to FFh (full scale) without overflow indication if greater. An input voltage equal to, or lower than VSSconverts to 00h. The conversion is monotonic: the results never decrease if the analog input does not and never increase if the analog input does not.

The 8-bit conversion is accurate to within 2 LSB. The minimal conversion time is 32 ADC clock cycles (16µs if A/D clock frequency at 2 MHz). The A/D converter clock is generated from the CPU clock divided by 2.

The high and low level reference voltages are connected to VDDand VSS. Conversion accuracy may therefore be degraded by voltage drops and noise in the event of heavily loaded or badly decoupled power supply lines.

The A/D converter is not affected by WAIT mode but, in power sensitive applications, it can be disabled before entering this mode. When the MCU enters HALT mode with the A/D converter enabled, the A/D clocks are stopped and the converter is disabled until the HALT mode is exited and the start-up delay has elapsed. A stabilisation time is also required before accurate conversions can be performed.

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4.6.3 Register Description A/D CONTROL/STATUS REGISTER (CSR)

Address: 0071h — Read/Write Reset Value: 00 h

b7: COCO

Conversion Complete.

COCO is set as soon as a new conversion can be read from the Result Data Register. COCO is cleared by reading the result or writing to the A/D Converter Control/Status Register.

b6: Reserved, must be programmed to 0 b5: ADON

A/D converter On

ADON allows the A/D converter to be switched on and off in order to reduce consumption when needed. When turned on (ADON = 1), a delay time (typically 10µs) is necessary for the ADC to stabi-

lize. Conversions may be inaccurate during this period.

b4 - b3: Reserved, must be programmed to 0. b2-0: CH2-CH0

Channel Selection

These bits select the analog input to convert, 000 selecting AIN0 and 111 selecting AIN7 (fewer than 8 lines may be available, depending on device specifications: see Block Diagram).

A/D DATA REGISTER (DR)

Address: 0070h — Read Only Reset Value: (undefined)

b7-0: AD7-AD0

Analog Converted Value

This register contains the converted analog value in the range 00h to 0FFh

COCO 0 ADON 0 0 CH2 CH1 CH0

AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0

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ST7285C

4.7 RDS FILTER

The Radio Data System (RDS) Filter peripheral consists of a Switched Capacitor (SC) bandpass filter centered on 57 KHz. This filter selects the RDS components from the multiplex radio signal. The filter output is directly used by the demodulator. The comparator limits the signal to digital levels. The comparator output feeds the RDS demodulator.

4.7.1 Features

– 57KHz Switched Capacitor (SC) bandpass filter – Comparator – D/A converter for comparator Offset Compensa-

tion by software

– Power Down mode.

Figure 32. RDS Filter Block Diagram

FISEL

PHI1

ADR

RESET

RDSREF

INTERFACE

TEST MODE

SELECTOR

D/A CONVERTE R

(Offset-compensation)

Comparator

RDSCOMP

STOP

CLKIN

(4.332MHz)

RDSFIL

TM2TM

SMOOTHING

FILTER

PREFILTER

(ANTI-

BUFFER

8th ORDER

SC FILTER

ALIASING)

MPX

to Demodulator

10µF

270p

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RDS FILTER (Cont’d)

4.7.2 Functional Description

The RDS filter is of classical Switched Capacitor type, comprising: an anti-aliasing filter, the SC-filter proper and a smoothing filter connected in cascade. The block diagram is given inFigure 33.

The Filter peripheral is composed of the following functional blocks:

–

Prefilter

. The anti-aliasing filter consists of a 2

order Sallen-Key filter. The phase response in the passband is linear. The cut-off frequency is located at about 360KHz. The prefilter includes an operational amplifier with a gain of 80 dB.

– SC Filter. The SC filter is a 8thorder bandpass

filter. It comprises 4 cascaded biquads. The biquads all have the same scheme and differ only in their capacitor values. The switches are controlled by a clock generator which produces nonoverlapping clock phases.

– Buffer. The output of the SC-Filter cannot be

connected toresistive loads, since this would severely reduce its gain. A buffer is therefore connected between the SC filter and the smoothing filter.

– Smoothing filter. The smoothing filter connect-

ed to the Sc-filter (through the Buffer) is a simple RC low pass filter. The output is connected to RDSFIL pin (external connection) and to the Comparator.

–

Comparator

. The comparator is connected to the smoothing filter and is able to detect zerocrossing in less than 125ns. The digital output of the comparator is connected via a port to the RDS demodulator.

– D/A Converter. A maximum offset of 1mV is al-

lowed on the comparator’s inputs. The offset compensation is achieved as follows: in a software selectable test mode, the input of the filter is switched to RDSREF (=2.5V). The D/ A converter register (RDSFi1) is set to zero and then incremented by software until the comparator changes its sign.

–

Test Mode Selector

. This function is controlled via 4 bits in the filter control register (RDS Fi2). It selects the various test modes. (see next point).

– ST7 interface registers. These are described

below.

RDS Fi1

Address 005Ah: — Read/Write Register

b7 = reserved. b6 = COMP Comparator output (read only). b5-0 =

AD5-AD0

Offset correction value output by D/A (1LSB=2mV).

RDS Fi2

Address 005Bh — Read/Write Register

b7-5 = reserved. b4 = PDB Power down bit (1 = Run; 0 = Power-down) b3-0 = TM3-TM0 Mode select. Only Modes shown in the table below

are valid; other modes are reserved.

When the internal filter is switched off, the RDSCOMP pin can be used as an input and to feed the demodulator from an external filter.

76 543210

- COMP AD5 AD4 AD3 AD2 AD1 AD0

7 6 543210

- - - PDB TM3 TM2 TM1 TM0

TM3 TM2 TM1 TM0 Mode

0000filter off (reset state) 0011normal operating mode

1101

offset compensation mode

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ST7285C

4.8 RDS DEMODULATOR

The RDS demodulator is a fully digital Radio Data System demodulator. The module includes 57KHz carrier recovery, RDS clock (1187.5Hz) recovery, bi-phase decoder, fast ARI indicator and signal quality indicator. the module is controlled through ST7 registers. The RDS signal is fed in through the pin RDSCOMP. The reference frequency is derived from the ST7 quartz oscillator. Therefore, the quartz frequency must be 8.664MHz.

4.8.1 Features

– Pure digital RDS demodulator without external

components.

– Phase polarity data extractor. – Phase integral data extractor.

– Data extractor selectable:

a) automatically via quality detector; b) via software.

– Selectable quality indicator:

a) RDS signal quality;

b) polarity difference and integral data. – Selectable time constant for 57KHz PLL. –Selectable inhibit of PLL regulation to be used for

AF tests and temporary field strength weakness (i.e. tunnels or other obstacles to radio reception).

– Fast ARI indicator, controlled by software.

Figure 33. RDS Demodulator Block Diagram

0 1

RDSCOMP

arp

aren

lock

upr

qen

lck1 lck0

57KHz PLL

Fast ARI Indicator

“Polarity” Bi-phase

Decoder

“Integral” Bi-phase

Decoder

Differential

Decoder 1

dat1

Differential

Decoder 2

dat2

sdat

RDS Dat

qual2

Quality

Detector

qual1

lck3 lck2

squal

RDS Clock

QUALITY

1187.5Hz Bit PLL

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ST7285C

RDS DEMODULATOR(Cont’d)

4.8.2 Functional Description

The RDS Demodulator is fed with a 57KHz bandpass filtered and limited multiplex signal.

It contains the following functional blocks: – 57kHz PLL. This circuit is implemented as a var-

iable counter controlled by a “COSTAS” phase comparator. Toachieve fast lockup time, thelowpass filter features four software selectable time constants. Following a reset, the longest time constant is selected and used for the locked condition. The time constant relates to the time needed to compensate a 90 degree phase deviation. As the PLL locks to 0 and 180 degrees, whatever is closest, this is the maximum possible phase deviation. The selectable time constants are listed in the following register description.

– 1187.5Hz PLL. This circuit detects zero cross-

ings of the phase of the input signal. After low pass filtering, this information is used to control a variable divider, which generates the RDS clock. The time constant ofthe low pass filter is also selectable in four steps. The regulation of both PLLs may be inhibited by software. This may be used to “freeze” the actual phase relation in order to bridge a certain time of weak or non-existing input signal. (e.g. during AF tests, breakdown in field strength,...). Depending of the precision of the quartz oscillator some seconds of weak input signal may be spanned without loosing the lock condition.

– “Polarity” Phase Decoder. With the help o the

recovered 57kHz carrier, the sign of the input signal phase is integrated over one bit (48 samples).

– “Integral” Phase Decoder. The relative phase

angle of the input signal to the recovered carrier

is measured. Again 48 samples are accumulated. Regarding of the “polarity phase decoder, this system is less sensitive to the precision of the recovered carrier, but is more sensitive with respect to ignition spikes.

– Differential Decoder.Every phase decoder out-

put is fed into its own differential decoder. For error correction purposes, a quality bit can be generated in order to mark all differences between the two decoder outputs.

–

Quality Detector

.This unit measures the amount of opposite phase samples. With anerror free signal; every bit consists of 24 positive and 24 negative phase samples related to thecarrier. Dueto noise, this balance may be disturbed. all bits with a relation greater than 40 to 8are marked as bad. This quality information may be used by the software foran improved error correction. It also may be used internally (selection by software) to switch automatically between “polarity” and “integral” phase decoders. The source of RDS data may be one or the other output of these two decoders. The source of the quality output may be selected from the quality detector or from the exor which builds the difference between the two differential decoders.

– ARI Indicator.In order to receive a correct RDS

signal,the57KHzPLLregulationmustbechanged inaccordance withthepresenceofARI.Therefore a fast ARI indicator is implemented. This function may be optionally taken over by software.

–

Interface Registers

. These allow control of the Demodulator circuit by the MCU. Register descriptions are given below:

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ST7285C

RDS DEMODULATOR(Cont’d) RDS DE1

Address 005Ch Reset Value: 0000 0000b

b7 = lock Inhibits regulation of PLLs to keep the current

phase value during weak signal conditions. 0: normal regulation (Reset Value)

1: inhibit regulation. b6-5 = lck3 - lck2 Select time constant for 1187.5Hz PLL.

b4-3 = lck1 - lck0 Select time constant of 57KHz PLL.

b2 = QEN Enables automatic selection of input to differential

decoder 1. 0 = enable selection by quality (Reset Value) 1 = disable selection b1 = SDAT Selectsdifferentialdecoder fortheRDSdataoutput. 0 = differential decoder 1 (Reset Value) 1 = differential decoder 2. b0 =

SQUAL

Selects quality for the quality output. 0 = from the quality detector (qal1) (Reset Value) 1 = exclusive OR of differential decoders (qal2).

RDS DE2 — Address 005D h Reset Value: 0xxx xxxxb

b7 = UPR Software reset to various demodulator parts. 0 = normal run mode (Reset Value)

1 = demodulator reset. After wring this bit to one, a reset pulse will be gen-

erated. The bit will then be automatically reset to zero. This bit is always read as a zero.

b6 = QAL Output of the quality detector which is actually de-

tected. This bit is fed into the RDS-GBS module. b5 = QAL1 Output of the quality detector. b4 =

QAL2

Resulant of XOR of dat1 and dat2. b3 = DAT RDS-dat output which is actually detected. This bit

is fed into the RDS-GBS module. b2 = DAT1 Output of the phase polarity data extractor. b1 =

DAT2

Output of the phase integral data extractor. b0 = CLK RDS clock output (1187.5Hz)

7 654321 0

lock lck3 lck2 lck1 lck0 qen sdat squal

lck3 lck2

lock time needed for max (90

°)

deviation

0 0 160ms (Reset Value) 0 1 80ms 1 0 40ms 1 1 20ms

lck1 lck0

lock time needed for max (90

°)

deviation

0 0 16ms(Reset Value) 0 1 8ms 1 0 4ms 1 1 2ms

UPR QAL QAL1 QAL2 DAT DAT1 DAT2 CLK

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ST7285C

RDS DEMODULATOR(Cont’d) RDS DE3 — Address 005E h

Reset Value: xxxx x000b

b7-3 = reserved. b2 = ARI ARI indicator. 0 = pure RDS, no ARI (Reset Value) 1 = RDS plus ARI. Note that this bit is simply an indicator. b1 = AREN Selects software or hardware ARI indication. 0 = internally by hardware (Reset Value) 1 = forced by software according to ARP bit. b0 = ARP Preset ARI indication. 0 = ARI (Reset Value) 1 = pure RDS without ARI.

RDS DE4 — Address 005F h Reset Value: 0xx0 0000b

b7 = DETM Selects test mode when set to “1”. This bit must be

kept in the reset state (“0”) for normal operation. b6-5 = reserved. b4-1 = TE4-TE1 RESERVED. These bits are for internal test use

only: they must be kept in the reset state (all “0”) for normal operation

b0 = NDEPOR Enables the module 0 = module disabled (Reset Value) 1 = module enabled (normal operating mode).

- - - - - ARI AREN ARP

DETM - - TE4 TE3 TE2 TE1

NDE-

POR

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4.9 RDS G.B.S

4.9.1 Introduction

The main task of the GBS module is to acquire Group and Block Synchronization of a received RDS data steam, which is provided in a modified shortened cyclic code.

In order to achieve synchronization, a syndrome is calculated on every data clock pulse. Detection of a valid syndrome is indicated by flag VSI with associated interrupt, while the corresponding block is kept in BL(0:2). Starting in BIT_SYNC mode the SW can use CNA zero count interrupt (CNA=1) and VSI check for synchronization phase. If the synchronization criteria is fulfilled, the SW can switch to BLK_SYNC mode, setting counter CNA to 26 and CNB to the current block code. The SW maintains block synchronization easily by checking VSI and ORD, which indicates a correct block order.

An optional GRP_SYNC mode can be entered for RDS standby operation using the appropriate counter interrupt selection.

The combination of software triggered syndrome calculation, a second 26-bit shift register and a 26bit quality register, allow highly flexible error correction by software.

Single quality errors, representing a 1 or 2 bit RDSDAT error, are indicated by the SQE flag. They can be corrected by SW with high security.

4.9.2 Features

– Hardware implemented decoding of RDS data

stream.

– Hardware triggered syndrome calculation with

every rising edge of RDSCLK.

– Storage of 26 RDS bits (1 block). – Fast syndrome calculation

(within 2.4µsatf

OSC

=8.664MHz).

– 5-bits RDS-counter CNA and 2-bit RDS-block

counter CNB.

– Selectable counter interrupt for BIT/BLOCK/

GROUP-SYNC mode.

– “Valid Syndrome” detection unit with interrupt

and block code output.

– Selectable MMBS Radio Paging option for block

E syndrome detection.

– “Valid Block Order” flag. – Extended “error correction by software” support. – Software triggered syndrome calculation. – Parallel storage of 26 RDSDAT bits and 26

QUALITY bits for high flexibility.

– Single/Multiple quality-error flags.

Figure 34. Principles of Baseband Coding

BLOCK1

BLOCK2 BLOCK3

BLOCK4

GROUP = 4 BLOCKS = 104 BITS

m15m14m13m12m11m10m9m8m7m6m5m4m3m2m1m

’

BLOCK = 26BITS

INFORMATION WORD =16-BITS

CHECK WORD = 10-BITS

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ST7285C

RDS G.B.S. (Cont’d) Figure 35. G.B.S. Block Diagram

ADDRESS

DECODER

ST7 INTERFACE

addresses

TIMING GENERATOR

addr8

addr9 addr10 addr11

addr12 addr13 addr14

addr15

addr0

addr1 addr2 addr3

26-bit QUALITY register

QR0...QR3

26-bit RDSDAT register

DR0...DR3

26-bit shift register

SR0...SR3

10-bit polynomial shift

SY0...SY1

Syndrome Detection

& Block Coder

Block Order

5-bit

count register

CNA

2-bit

count register

CNB

irq

vse

cni

rdsclk

cnaz

cnbz

ORD

vsi

nckpoly

clkshift

Sin

addr4

addr5

addr4

addr6

Fosc(8.664MHz)

Itsync

Phi1(4.332MHz)

A[3:0]

Nsyncsel

R/W Reset

D[7:0]

DATA

clock

nclock

clock

Sin

RDSDAT

RDSCLK

QUAL

Circuit

BL[2:0]

Compare Circuit

autoreload

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ST7285C

RDS G.B.S. (Cont’d)

4.9.3 Functional Description

4.9.3.1 Principles of Baseband Coding

Figure 34 illustrates the principles of baseband coding. The largest element in the structure is called a “group”. Each group contains 4 blocks of 26 bits each. Each block contains an information word (16 bits) and a check-word (10bits).

The basic baseband data rate e is 1187.5 bits/s. The baseband is a modified shortened cyclic code, that means the transmitted vector c(x) is given by:

c(x) = d(x) +m(x)*x10+ {m(x)*x10}/d(x) |

mod g(x)

where, m(x) represents the 16-bit message vector:

m(x) = m

15*

x15+m

14*

x14+...+ m1*x1+m0*x

g(x) represents the polynomial generator:

g(x) = x10+x8+x7+x5+x4+x3+1

and d(x) represents the offset word according to the values tabulated inTable 9 below.

For more information about the theory and implementation of the modified shortened cyclic code, please refer to the specification of the European Broadcasting Union.

4.9.3.2 Hardware Configuration

The GBS circuit comprises the following functional blocks; these are shown schematically in the Block Diagram, Figure 35.

–26-bit ShiftRegister(SR3-SR0), may act,either

as a straight 26-bit delay or as a recirculating shift register. On each rising edge of RDSCLK a new RDS-bit isshifted into the register. Then, the contentsof the shiftregister are rotated 26 times(one circuit) for syndrome calculation. In error correction mode (ECM=1), the shift registeractsonly asacircular register. New RDS-bits are not shifted in. They are stored in the parallel shift register DR0- DR3.

– Polynomial Divisioncircuit, comprising a 10-bit

shift register (SY0- SY1) with feedback taps for

syndrome calculation. During the rotation of the shift register the RDS-bits are passed serially into the polynomial division register where the syndrome is calculated and stored.

–

Syndrome Detection

circuit, compares the calculated syndrome with a 5(6)-word syndrome ROM. The output consists of the block code BL[2:0] and the VSI flag with its associated interrupt. VSI is high when avalidsyndrome is detected. Detection of offset syndrome, E, is enabled by control bit US.

–5-bitCounter(CNA), countsdown onevery rising

edge ofRDSCLK.The counterreload register can be written by software. On zero count, it restarts immediately with the value of the reload register and can generate an interrupt on zero count. This counter is used as RDS-bit counter (26...1).

–

2-bit Counter

(CNB), counts down on every zero count of CNA. The counter can be written by software. CNB is running free and can generate an interrupt. This counter is used as RDS-block counter (3...1)

–

Timing Generator

block comprising a modulo28 counter with end stops and some combinational logic. The modulo-28 counter is used to generate one shift clock, 26 rotate clocks and one end of calculation clock. In error correction mode (ECM=1) the shift clock is masked.

– 26-bit RDSDAT register (DR3-DR0), in parallel

to shift register SR3-SR1. It works in straight shift mode only. On each rising edge of the RDSCLK the RDSDAT-bit is shifted into the register. This register is used for temporary block storage during error correction.

– 26-bit QUALITY register (QR3-QR0), works in

straight shift mode only. On each rising edge of the RDSCLK the QUALITY bit coming from the demodulator is shifted into the register.

Table 9. Offset Words and their corresponding Syndromes

Offset

(block)

Block code

2BL1BL0

Offset word

9,d8,d7

,...,d

Syndrome

9,d8,d7

,...,d

A 0 1 0 0011111100 1111011000 B 0 0 1 0110011000 1111010100

C 1 0 0 0101101000 1001011100

C’ 0 0 0 1101010000 1111001100

D 0 1 1 0110110100 1001011000

E 1 0 1 0000000000 0000000000

WRONG 1 1 1 all others all others

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ST7285C

RDS G.B.S. (Cont’d)

4.9.3.3 GBS Registers

Sixteen registers are dedicated to interfacing the Group and Block Synchronization module to the CPU.

These registers, together with their symbolic names, bit names and address are presented in tabular form in Table 10 below and are here described in greater detail.

Register Reset States: all registers bits are set to “0” during Reset, except for CNA4-CNA0, CNB1, CNB0 and ORD, which are set to “1”.

SRx - Shift Registers

b7,6 =

SR0:

contain the 2 last transmitted bits

c1’,c0’ of the checkword. b5-0 are not used and are always read as “0”. b7-0 =

SR1:

contain the 8 first transmitted bits

(c9’...c2’) of the checkword. b7-0 =

SR2:

contain the 8 last information bits

(m7’...m0’) of the message vector.

b7-0 = SR3: contain the 8 first information bits (m15’...m8’) of the message vector.

SY0 - Polynomial Register 0

b7,6 = SY0: contain the 2 least significant bits of the calculated syndrome. For valid syndromes, these two bits are “0.

b5 is not used, and is always read as “0”. b4 = US (USA option). Setting US to “1” enables

detection of block E. b3 = ORD flag. Set to “1” when block counter

CB[1:0] is equal to block code BL[1:0]: otherwise it is “0”. Stable with VSI or CNI. Read only. Reset Value is one.

b2-0 =

BL[2:0]

block code, see Table 9. Stable

with CNI or VSI. Read only.

SY1 - Polynomial Register 1

b7-0 =

SY1:

contain the 8 most significant bits

(p9’...p2’) of the calculated syndrome.

Table 10. GBS Register Map

SR0 - shift reg. 0 0060h c

’c

’------

SR1 - shift reg. 1 0061h c

’c

’

SR2 - shift reg. 2 0062h m

SR3 - shift reg. 3 0063h m

SY0 - polynomial reg. 0 0064h p

- US ORD BL2 BL1 BL0

SY1 - polynomial reg. 1 0065h p

GS_CNT - count reg. 0066h CNB1 CNB0 SYNC CNA4 CNA3 CNA2 CNA1 CNA0

GS_INT - interrupt reg. 0067h CAL CAR ECM VSI VSE CNI CE1 CE0

DR0 - RDSDAT reg. 0 0068h DR1 DR0 - MQE SQE QAL RCL RDA DR1 - RDSDAT reg. 1 0069h DR9 DR8 DR7 DR6 DR5 DR4 DR3 DR2 DR2 - RDSDAT reg. 2 006Ah DR17 DR16 DR15 DR14 DR13 DR12 DR11 DR10

DR3 - RDSDAT reg. 3 006Bh DR25 DR24 DR23 DR22 DR21 DR20 DR19 DR18 QR0 - QUALITY reg. 0 006Ch QR1 QR0 - - - - - QR1 - QUALITY reg. 1 006Dh QR9 QR8 QR7 QR6 QR5 QR4 QR3 QR2 QR2 - QUALITY reg. 2 006Eh QR17 QR16 QR15 QR14 QR13 QR12 QR11 QR10 QR3 - QUALITY reg. 3 006Fh QR25 QR24 QR23 QR22 QR21 QR20 QR19 QR18

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ST7285C

RDS G.B.S. (Cont’d) GS_CNT - Count Register

b7-6 = CNB[1;0]

free-running 2-bit counter

; used as block/order counter. It is decremented on zerocount of CNA[4:0]. The zero-counts of CNA and CNB are used for counter interrupt generation. Reset Value equals one.

b5 =

SYNC:

Set to “1” whenever CNA[4;0] reaches a zero-count. it is valid for one period of RDSCLK. Read only. SYNC flag is used when a counter interrupt is desired on every RDSCLK (used for general timing or ARI filter service), while the BLK-SYNC interrupt service is performed every 26 bits (CNA=26).

b4-0 = CNA[4:0]:

5-bit r/w autoreload counter;

used as RDS bit counter

. It is decremented on every rising edge of RDSCLK. When writing to CNA, both a latch and the counter itself are written. Immediately after reaching zero-count, the contents of the latch are loaded back into the counter (autoreload), so the zero-count state can never be read by software. The zero-count of CNA is used for counter interrupt generation. Reset Value equals one.

GS_INT - Interrupt Register

b7 =

CAL

Start Calculation.

Writing a “1” into CAL leads to a new syndrome calculation. CAL is always read as “0”. Used in software error correction.

b6 = CAR:

Calculation Running

. Set to “1” by writing CAL=1. It returns to “0” when the syndrome calculation is complete (VSI valid). Read only. Used in software error correction.

b5 =

ECM:

Error Correction Mode.

If error correction by software is to be performed, ECM must be set to “1”. This suppresses both shift and rotate clocks for shift registers SR3-SR0, making them available for software-triggered syndrome calculations which may require more than one RDSCLK period. On completion of a correction, ECM must be reset to “0” and the current status of SR3-SR0 must be retrieved from the shadow registers DR3DR0 by a copy routine.

b4 =

VSI:

Valid Syndrome Interrupt

. This flag is set to “1” when the block code (BL[2:0]) is equal to one of the six valid syndromes. Otherwise, it is reset to “0”. VSI is valid on completion of a syndrome calculation, for one period of RDSCLK. However, VSI must be reset by software at the end of the interrupt service routine. VSI and CNI interrupts are ORed to the active-high level interrupt, ITSYNC.

b3 = VSE:

Valid Syndrome interrupt Enable.

Set-

ting VSE to “1” enables the VSI interrupt. b2 = CNI:

Counter Interrupt

. This flag is set to “1”on the zero-count of CNA/CNB or on the rising edge of RDSCLK, depending on the setting of CNE[1:0]. CNI is valid on completion of the syndrome calculation, for one period of RDSCLK. However, CNI must be reset by software at the end of the interrupt service routine. VSI and CNI interrupts are ORed to the active high level interrupt ITSYNC.

b1,0 = CNE[1:0]. Enables and selects the counter interrupt, see Table 11 below:

Table 11. Counter Interrupt Source Selection

DR0 - RDSDAT Register 0

b7,6 =DR[1:0]. Receives RDSDAT sequence. b5 = reserved, always read as “0”. b4 = MQE:

Multiple Quality Error

. Set to “1” when 2 or more low quality bit are detected during the last block (26 bits). MQE is valid for one period of RDSCLK, starting with CNA zero-count and is reset by hardware at the end of this period.

b3 =

SQE:

Single Quality Error

. Set to “1” when a low quality bit is detected during the last block (26 bits). SQE is valid for one period of RDSCLK, starting with CNA zero-count and is reset by hardware at the end of this period.

b2 = QAL. Transparent QUALITY input signal from RDS demodulator; read only.

b1 = RCL. Transparent RDSCLK input signal from RDS demodulator; read only.

b0 =

RDA

. Transparent RDSDAT input signal from

RDS demodulator; read only.

DRx - RDS Data Registers DR1. b7-0 contain bits 9-2 of a received RDSDAT

sequence. DR2. b7-0 contain bits 17-10 of a received RDS-

DAT sequence. DR3. b7-0 contain bits 18-25 of a received RDS-

DAT sequence.

CNE1 CNE0 Counter Interrupt Source Selection

0 0 counter interrupt disabled 01

counter interrupt onevery rising edge of RDSCLK

counter interrupt on CNA zero-count state

counter interrupt on CNA& CNB zero count states

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RDS G.B.S. (Cont’d) QR0 - Quality Register

b7-6 = QR[1:0] Receives QUALITY sequence. b5-0 = reserved; always read as “0”.

QRx - Quality Registers QR1. b7-0 contain bits 9-2 of a received QUALITY

sequence.

QR2.

b7-0 contain bits 17-10 of a received QUAL-

ITY sequence.

QR3.

b7-0 contain bits 25-18 of a received QUAL-

ITY sequence.

4.9.4 Acquisition of Group and Block Synchronization

New group and block synchronization is necessary after switching on the receiver, on tuning to a new station, or after a prolonged signal fade. The syndrome is calculated for every single received RDS-data bit. All valid syndromes corresponding to offset words A to E are shown inTable 9.

Blocks within each group are identified by offset words A, B, C or C’, and D. This fact is used for block and group synchronization. Detection and coding of block E is enabled by control bit US in Polynomial Register 0. Block E is used for additional Radio Paging Information in North America. For detailed information, see United States RDBS Standard Specification, published by NRSC.

4.9.5 Application Tips

It is recommended not to load CNA with “0”, because this would generate a CNAzero-count interrupt after every syndrome calculation, initiated either by positive edge of RDSCLK or by writing a “1” to CAL.

All data and flags are derived from the positive edge of RDSCLK and thus are only valid for one period of this clock.

All interrupt service routines (VSI or CNI interrupts) must be completed before the next positive edge of RDSCLK (i.e. within 842ms), except when Error Correction Mode is selected (ECM=1). In this case, the interrupt service may take up to 21.9ms in BLOCK_SYNC mode.

4.9.6 Block Synchronization Software

There are many strategies to achieve RDS Block Synchronization, A standard method with a simplified synchronization criteria is briefly described.

The software starts in BIT-SYNC mode. CNA is loaded with “1” and the counter interrupt is enabled on CNA zero-count. On each interrupt, the syndrome is checked via the VSI flag until VSI is

“1”. Then the blockcode BL[2:0] and the CNA count are saved; the software continues until the next Valid Syndrome detection.

If bit distance (26) and block order are correct, the RDS Block Synchronization is achieved, and the software can switch to BLOCK_SYNC mode. The software can easily maintain Block Synchronization by checking the VSI and ORD flags, the latter indicates correct block order.

This method does not respect dummy syndromes (valid syndromes appearing between two valid blocks).

An optional GRP_SYNC mode may be entered for RDS standby operation, using the appropriate counter interrupt selection.

4.9.7 Error Correction software

Software triggered syndrome calculation, a second 26-bit shift register and a 26-bit quality register, allow highly flexible error correction by software, using the quality signal information from the RDS demodulator.

A quality “low” state indicates an uncertain corresponding RDSDAT bit. Because of the differential decoding of RDSDAT, not only the RDSDAT bit pointed to by Quality, but also the following RDSDAT bit may be wrong. Thus a single quality error can represent a single or a double data bit error. A single quality error within one block is indicated by the SQE flag, multiple quality errors within one block are indicated by the MQE flag.

The software starts error correction by setting ECM to “1”, to make the main shift registers SR3SR0 available for software triggered syndrome calculations, which may take longer than one period of RDSCLK (842ms).

New incoming RDSDAT-bits are stored in the parallel shift registers DR3-DR0. Moreover, the current contents of the quality registers QR3-QR0, must be saved in RAM, in order to be used for the following error correction.

Error correction may be performed by reversing the RDSDAT bits in shift registers SR3-SR0, which are indicated as bad in the quality register (with respect to RDSDAT differential decoding). After each reverse, a new syndrome calculation is started (CAL=1) and checked (VSI). Single quality errors, representing a 1 or 2 bit RDSDAT error may be corrected with high security.

On completion of the correction, the contents of DR3-DR0 must be copied back into shift registers SR3-SR0, and ECM must be set to “0”.

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5 SOFTWARE

5.1 ST7 ARCHITECTURE

The 8-bit ST7 Core is designed for high code efficiency. It contains 6 internal registers, 17 main addressing modes and 63 instructions. The 6 internal registers include 2 index registers, an accumulator, a 16-bit Program Counter, a stack pointer and a condition code register. The two Index registers X and Y enable Indexed Addressing modes with or without offset, along with read-modify-write type data manipulations. These registers simplify branching routines and data modifications.

The 16-bit Program Counter is able to address up to 64K of ROM/EPROM memory. The 6-bit Stack Pointer provides access to a 64-level Stack and an upgrade to an 8-bit Stack Pointer is foreseen in order to be able to manage a 256-level Stack. The Core also includes a Condition Code Register providing 5 Condition Flags that indicate the result of the last instruction executed.

The 17 main Addressing modes, including Indirect Relative and Indexed addressing, allow sophisticated branching routines or CASE-type functions. The Indexed Indirect Addressing mode, for instance, permits look-up tables to be located anywhere in the address space, thus enabling very flexible programming and compact C-based code.

The 63-instruction Instruction Set is 8-bit oriented with a 2-byte average instruction size. This Instruction Set offers, in addition to standard data movement and logic/arithmetic functions, byte multiplication, bit manipulation, data transfer between Stack and Accumulator (Push/Pop) with direct stack access, as well as data transfer using the X and Y registers.

5.2 ST7 ADDRESSING MODES

The ST7 Core features 17 different addressing modes which can be classified in 7 main groups:

The ST7 Instruction set is designed to minimize the number of bytes required per instruction: To do so, most of the addressing modes may be subdivided in two sub-modes called long and short:

– The long addressing mode is the most powerful

because it can reach any byte in the 64kb addressing space, but the instruction is bigger and slower than the short addressing mode.

– The short addressing mode is less powerful be-

cause it can generally only access page zero (0000 - 00FFh range), but the instruction size is more compact, and faster. All memory to memory instructions are only working with short addressing modes (CLR, CPL, NEG, BSET, BRES, BTJT, BTJF, INC, DEC, RLC, RRC, SLL, SRL, SRA, SWAP)

Both modes have pros and cons, but the programmer does not need to choosewhich one is the best: theST7Assemblerwillalwayschoosethebestone.

Addressing Mode Example

Inherent nop Immediate ld A,#$55 Direct ld A,$55 Indexed ld A,($55,X) Indirect ld A,([$55],X) Relative jrne loop Bit operation bset byte,#5

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ST7 ADDRESSING MODES(Cont’d) Table 12. ST7 Addressing Mode Overview:

Mode Syntax Destination Ptr addr Ptr size Lngth

Inherent nop + 0 Immediate ld A,#$55 + 1 Short Direct ld A,$10 00..FF + 1 Long Direct ld A,$1000 0000..FFFF + 2 No Offset Direct Indexed ld A,(X) 00..FF + 0 Short Direct Indexed ld A,($10,X) 00..1FE + 1 Long Direct Indexed ld A,($1000,X) 0000..FFFF + 2 Short Indirect ld A,[$10] 00..FF 00..FF byte + 2 Long Indirect ld A,[$10.w] 0000..FFFF 00..FF word + 2 Short Indirect Indexed ld A,([$10],X) 00..1FE 00..FF byte + 2 Long Indirect Indexed ld A,([$10.w],X) 0000..FFFF 00..FF word + 2 Relative Direct jrne loop PC+/-127 + 1 Relative Indirect jrne [$10] PC+/-127 00..FF byte + 2 Bit Direct bset $10,#7 00..FF + 1 Bit Indirect bset [$10],#7 00..FF 00..FF byte + 2 Bit Direct Relative btjt $10,#7,skip 00..FF + 2 Bit Indirect Relative btjt [$10],#7,skip 00..FF 00..FF byte + 3

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ST7 ADDRESSING MODES(Cont’d) Inherent:

All related instructions are single byte ones. The op-code fully specify all required information for the CPU to process the operation. These instructions are single byte ones.:

Immediate:

The required data byte to do the operation is following the op-code. These are two byte instructions, one for the op-code and the other one for the immediate data byte.

Direct (short, long):

The data byte required to carry out the operation is found by its memory address, which follows the op-code.

The direct addressing mode consists of two submodes:

Direct (short):

The address is a byte, thus require only one byte after the op-code, but only allow 00 - FF addressing space.

Direct (long):

The address is a word, thus allowing 64Kb addressing space, but requires 2 bytes after the opcode.

Inherent Instruction Function

NOP No operation TRAP S/W Interrupt

WFI

Wait For Interrupt (Low Power Mode)

HALT

Halt Oscillator (Lowest Pow-

er Mode) RET Sub-routine Return IRET Interrupt Sub-routine Return SIM Set Interrupt Mask RIM Reset Interrupt Mask SCF Set Carry Flag RCF Reset Carry Flag RSP Reset Stack Pointer LD Load CLR Clear PUSH/POP Push/Pop to/from the stack INC/DEC Increment/Decrement TNZ Test Negative or Zero CPL, NEG 1 or 2 Complement MUL Byte Multiplication SLL, SRL, SRA, RLC,

RRC

Shift and Rotate Operations SWAP Swap Nibbles

Immediate Instruction Function

LD Load CP Compare BCP Bit Compare AND, OR, XOR Logical Operations ADC, ADD, SUB, SBC Arithmetic Operations

Available Long and

Short Direct Instructions

Function

LD Load CP Compare AND, OR, XOR Logical Operations

ADC, ADD, SUB, SBC

Arithmetic Additions/Substractions operations

BCP Bit Compare

Short Direct

Instructions Only

Function

CLR Clear INC, DEC Increment/Decrement TNZ Test Negative or Zero CPL, NEG 1 or 2 Complement BSET, BRES Bit Operations BTJT, BTJF Bit Test and Jump Operations SLL, SRL, SRA, RLC,

RRC

Shift and Rotate Operations

SWAP Swap Nibbles CALL, JP Call or Jump subroutine

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ST7 ADDRESSING MODES(Cont’d) Indexed (no offset, short, long)

The required data byte to do theoperation is found by its memory address, which is defined by the unsigned addition of an index register (X or Y) with an offset which follows the op-code.

The indirect addressing mode consists of three sub-modes:

Indexed (no offset):

There is no offset, (no extra byte after the opcode), but only allows 00 - FF addressing space.

Indexed (short):

The offset is a byte, thus require only one byte after the op-code, but only allow 00 - 1FE addressing space.

Indexed (long):

The offset is a word, thus allowing 64Kb addressing space, but requires 2 bytes after the op-code.

Indirect (short, long):

The required data byte to do the operation is found by its memory address, located in memory (pointer).

The pointer address follows the op-code. The indirect addressing mode consists of two sub-modes:

Indirect (short):

The pointer address is a byte, the pointer size is a byte, thus allowing 00 - FF addressing space, and requires 1 byte after the op-code.

Indirect (long):

The pointer address is a byte, the pointer size is a word, thus allowing 64Kb addressing space, and requires 1 byte after the op-code.

No Offset, Long and

Short Indexed Instruc.

Function

LD Load CP Compare AND, OR, XOR Logical Operations

ADC, ADD, SUB, SBC

Arithmetic Additions/Substractions operations

BCP Bit Compare

No Offset and Short

Indexed Inst. Only

Function

CLR Clear INC, DEC Increment/Decrement TNZ Test Negative or Zero CPL, NEG 1 or 2 Complement BSET, BRES Bit Operations BTJT, BTJF Bit Test and Jump Operations SLL, SRL,SRA, RLC,

RRC

Shift and Rotate Operations

SWAP Swap Nibbles CALL, JP Call or Jump subroutine

Available Long and Short

Indirect Instructions

Function

LD Load CP Compare AND, OR, XOR Logical Operations

ADC, ADD, SUB, SBC

Arithmetic Additions/Substractions operations

BCP Bit Compare

Short Indirect

Instructions Only

Function

CLR Clear INC, DEC Increment/Decrement TNZ Test Negative or Zero CPL, NEG 1 or 2 Complement BSET, BRES Bit Operations BTJT, BTJF Bit Test and Jump Operations SLL, SRL, SRA,

RLC, RRC

Shift and Rotate Operations

SWAP Swap Nibbles CALL, JP Call or Jump subroutine

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ST7 ADDRESSING MODES(Cont’d) Indirect Indexed (short, long):

This is a combination of indirect and short indexed addressing mode. The required data byte to do the operation is found by its memory address, which is defined by the unsigned addition of an index register value (X or Y) with a pointer value located in memory. The pointer address follows the op-code.

The indirect indexed addressing mode consists of two sub-modes:

Indirect Indexed (short):

The pointer address is a byte, the pointer size is a byte, thus allowing 00 - 1FE addressing space, and requires 1 byte after the op-code.

Indirect Indexed (long):

The pointer address is a byte, the pointer size is a word, thus allowing 64Kb addressing space, and requires 1 byte after the op-code.

Relative mode (direct, indirect):

This addressing mode is used to modify the PC register value, by adding an 8 bit signed offset toit.

The relative addressing mode consists of two submodes:

Relative (direct):

The offset is following the op-code.

Relative (indirect):

The offset is defined in memory, which address follows the op-code.

Long and Short

Indirect Indexed

Instructions

Function

LD Load CP Compare AND, OR, XOR Logical Operations

ADC, ADD, SUB, SBC

Arithmetic Additions/Substractions operations

BCP Bit Compare

Short Indirect Indexed

Instructions Only

Function

CLR Clear INC, DEC Increment/Decrement TNZ Test Negative or Zero CPL, NEG 1 or 2 Complement BSET, BRES Bit Operations

BTJT, BTJF

Bit Test and Jump Operations

SLL, SRL, SRA, RLC, RRC

Shift and Rotate Opera-

tions SWAP Swap Nibbles CALL, JP Call or Jump subroutine

Available Relative

Direct/Indirect

Instructions

Function

JRxx Conditional Jump CALLR Call Relative

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5.3 ST7 INSTRUCTION SET

The ST7 family devices use an Instruction Set consisting of 63 instructions. The instructions may

be subdivided into 13 main groups as illustrated in the following table:

Using a pre-byte

The instructions are described with one to four opcodes.

In order to extend the number of available opcodes for an 8-bit CPU (256 op-codes), three different prebyte opcodes are defined. These prebytes modify the meaning of the instruction they precede.

The whole instruction becomes: PC-2 End of previous instruction PC-1 Prebyte PC Op-code PC+1 Additional word (0 to 2) according to the

number of bytes required to compute the effective address

These prebytes enable instruction in Y as well as indirect addressing modes to be implemented.

They precede the opcode of the instruction in X or the instruction using direct addressing mode. The prebytes are:

PDY 90Replace an X based instruction using im-

mediate, direct, indexed, or inherent addressing mode by a Y one.

PIX 92 Replace an instruction using direct, direct

bit, or direct relative addressing mode to an instruction using the corresponding indirect addressing mode. It also changes an instruction using X indexed addressing mode to an instruction using indirect X indexed addressing mode.

PIY 91 Replace an instruction using X indirect in-

dexed addressing mode by a Y one.

Load and Transfer LD CLR Stack operation PUSH POP RSP Increment/Decrement INC DEC Compare and Tests CP TNZ BCP Logical operations AND OR XOR CPL NEG Bit Operation BSET BRES Conditional Bit Test and Branch BTJT BTJF Arithmetic operations ADC ADD SUB SBC MUL Shift and Rotates SLL SRL SRA RLC RRC SWAP SLA Unconditional Jump or Call JRA JRT JRF JP CALL CALLR NOP RET Conditional Branch JRxx Interruption management TRAP WFI HALT IRET Code Condition Flag modification SIM RIM SCF RCF

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Mnemo Description Function/Example Dst Src H I N Z C

ADC Add with Carry A = A + M + C A M H N Z C ADD Addition A = A + M A M H N Z C AND Logical And A = A . M A M N Z BCP Bit compare A, Memory tst (A . M) A M N Z BRES Bit Reset bres Byte, #3 M BSET Bit Set bset Byte, #3 M BTJF Jump if bit is false (0) btjf Byte, #3, Jmp1 M C BTJT Jump if bit is true (1) btjt Byte, #3, Jmp1 M C CALL Call subroutine CALLR Call subroutine relative CLR Clear reg, M 0 1 CP Arithmetic Compare tst(Reg - M) reg M N Z C CPL One Complement A = FFH-A reg, M N Z 1 DEC Decrement dec Y reg, M N Z HALT Halt 0 IRET Interrupt routine return Pop CC, A, X, PC H I N Z C INC Increment inc X reg, M N Z JP Absolute Jump jp [TBL.w] JRA Jump relative always JRT Jump relative JRF Never jump jrf * JRIH Jump if Port B INT pin = 1 (no Port B Interrupts) JRIL Jump if Port B INT pin = 0 (Port B interrupt) JRH Jump if H = 1 H = 1 ? JRNH Jump if H = 0 H = 0 ? JRM Jump if I = 1 I = 1 ? JRNM Jump if I = 0 I = 0 ? JRMI Jump if N = 1 (minus) N = 1 ? JRPL Jump if N = 0 (plus) N = 0 ? JREQ Jump if Z = 1 (equal) Z = 1 ? JRNE Jump if Z = 0 (not equal) Z = 0 ? JRC Jump if C = 1 C = 1 ? JRNC Jump if C = 0 C = 0 ? JRULT Jump if C = 1 Unsigned < JRUGE Jump if C = 0 Jmp if unsigned >= JRUGT Jump if (C + Z = 0) Unsigned > JRULE Jump if (C + Z = 1) Unsigned <=

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LD Load dst <= src reg, M M, reg N Z MUL Multiply X,A = X * A A, X, Y X, Y, A 0 0 NEG Negate (2’s compl) neg $10 reg, M N Z C NOP No Operation OR OR operation A = A + M A M N Z POP Pop from the Stack pop reg reg M

HINZC

pop CC CC M PUSH Push onto the Stack push Y M reg, CC RCF Reset carry flag C = 0 0 RET Subroutine Return RIM Enable Interrupts I = 0 0 RLC Rotate left true C C <= A <= C reg, M N Z C RRC Rotate right true C C => A => C reg, M N Z C RSP Reset Stack Pointer S = Max allowed SBC Substract with Carry A = A - M - C A M N Z C SCF Set carry flag C = 1 1 SIM Disable Interrupts I = 1 1 SLA Shift left Arithmetic C <= A <= 0 reg, M N Z C SLL Shift left Logic C <= A <= 0 reg, M N Z C SRL Shift right Logic 0 => A => C reg, M 0 Z C SRA Shift right Arithmetic A7 => A => C reg, M N Z C SUB Substraction A = A - M A M N Z C SWAP SWAP nibbles A7-A4 <=> A3-A0 reg, M N Z TNZ Test for Neg & Zero tnz lbl1 N Z TRAP S/W trap S/W interrupt 1 WFI Wait for Interrupt 0 XOR Exclusive OR A = A XOR M A M N Z

Mnemo Description Function/Example Dst Src H I N Z C

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6 ELECTRICAL CHARACTERISTICS

6.1 ABSOLUTE MAXIMUM RATINGS

Devices of the ST72 family contain circuitry to protect the inputs against damage due to high static voltage or electric fields. Nevertheless, it is recommended that normal precautions be observed in order to avoid subjecting this high-impedance circuit to voltages above those quoted in the Absolute Maximum Ratings. For proper operation, it is recommended that VINand V

OUT

be constrained

within the range:

≤

VINand V

OUT

≤

To enhance reliability of operation, it is recommended to configure unused I/Os as inputs and to

connect them to an appropriate logic voltage level such as VSSor VDD.

All the voltage in the following tables are referenced to VSS.

Stresses above those listed as “Absolute Maximum Ratings” may cause permanent damage to the device. Functional operation of the device at these conditions is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.

Absolute Maximum Ratings (Voltage Referenced to VSS)

Symbol Ratings Value Unit

DD/VDDA/VDDP

Supply Voltage 0.3 to +6 V

DDA -VDD

| Supply Voltage < 50 mV

Input Voltage VSS- 0.3 to VDD+ 0.3 V

-I

Total current into VDD/VSSpins 50/20 mA

Current Drain per Pin Excluding V

and V

20 mA

Maximum Operating Temperature Range

to T

-40to +85

°C

STG

Storage Temperature Range -65 to +150 °C

High voltage on pins PH3, PH4, PH5

10 V

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6.2 POWER CONSIDERATIONS

The average chip-junction temperature, TJ, in degrees Celsius, may be calculated using the following equation:

TJ=TA+(PDxθJA)(1)

Where: –TAis the Ambient Temperature in°C, –θJAis the Package Junction-to-Ambient Thermal

Resistance, in°C/W,

–PDis the sum of P

INT

and P

I/O

–P

INT

is the product of I

DD andVDD

, expressed in

Watts. This is the Chip Internal Power

–P

I/O

represents the Power Dissipation on Input

and Output Pins; User Determined.

For most applications P

I/O<PINT

and may be ne-

glected. P

I/O

maybe significant if the device is con-

figured todrive Darlington basesorsinkLEDLoads.

An approximate relationship between PDand T

(if P

I/O

is neglected) is given by:

PD=K÷(TJ+ 273°C) (2)

Therefore:

K=PDx(TA+273°C) +θJAxP

(3)

Where:

– K is a constant for the particular part, which may

be determined from equation (3) by measuring PD(at equilibrium) for a known TA.Using this value of K, the values of PDand TJmay be obtained by solving equations (1) and (2) iteratively for any value of TA.

Table 13. Thermal Characteristics

Symbol Package Value Unit

θJ

PQFP80 60 °C/W

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6.3 DC ELECTRICAL CHARACTERISTICS

(TA= -40 to +85°C unless otherwise specified)

Note:

All voltages are referred to VSSunless otherwise specified.

Note:At85°C and VDD= 5.5V, code 255 is missing.

Note*):The 3rd harmonic (57KHz) must be less than -40dB with respect to the input signal plus gain

STANDARD I/O PORT PINS

Symbol Parameter Conditions Min Typ Max Unit

Input Low Level Voltage - - 0.3xV

Input High Level Voltage 0.7xV

--V

Output Low Level Voltage

I=-5mA - - 0.5 V

I=-1.6mA - - 0.3 V

Output Low Level Voltage on pins PH3, PH4, PH5

I=-5mA - - 1.0 V

I=-1.6mA - - 0.4 V

Output High Level Voltage

I=5mA 3.1 - - V

I=1.6mA 3.4 - - V

Input Leakage Current VSS<V

PIN<VDD

-10 - 10 µA

RPU

Pull-up Equivalent Resistance VIN=V

40 - 250 KW

ohl

Output H-L Fall Time Cl=50pF - 30 - ns

olh

Output L-H Rise Time Cl=50pF - 30 - ns

GENERAL

Symbol Parameter Conditions Min Typ. Max Unit

Supply Voltage

RDS Filter operational 4.5 5.5

Without RDS filter capability 3.0 6.0

A/D CONVERTER Symbol Parameter Conditions Min Typ Max Unit

Val Resolution f

OSC

= 8 MHz 8 bit

Terr Total Error f

OSC

=8MHz ±2 LSB

Tcon Conversion Time f

OSC

=8MHz 16 µs

Rva Analog Source Impedance - 10 KΩ

RDS FILTER Symbol Parameter Conditions Min Typ Max Unit

Center Frequency 56.5 57 57.5 KHz

BW 3dB Bandwidth V

: 3mV rms 2.5 3 3.5 KHz

G Gain @ 57 KHz 18 20 22 dB

A Attenuation

∆f=±4KHz f = 38KHz f = 67KHz

50 35

22 80 50

Input Impedance of MPX 100 160 200 KΩ

Load Impedance of FILOUT 1 MΩ

S/N Signal to Noise Ratio V

= 3mV

RMS

40 dB

MPX input signal f = 19KHz, T3 ≤ 40 dB

170 250 600 mV

RMS

REF

Reference VDD/2 V

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6.4 AC ELECTRICAL CHARACTERISTICS

(TA= -40 to +85°C unless otherwise specified)

6.5 CONTROL TIMING

(Operating conditions TA= -40 to +85°C unless otherwise specified)

Note: 1. The minimum period t

ILIL

should not be less than the number of cycle times it takes to execute the

interrupt service routine plus 21 cycles.

Symbol Parameter Condition s

Value

Unit

Min Typ. Max

Operating Supply Voltage 4.332 MHz Internal 4.5 5.5 V

Supply Current

RUN Mode f

EXT

= 8.664MHz

= 5.0V, f

INT

= 4.332MHz

WAIT Mode f

EXT

= 8.664MHz

= 5.5V, f

INT

= 4.332MHz

HALT Mode, V

= 5.0V

200

320

µA

Data Retention Mode HALT Mode 2 V

Symbol Parameter Conditions

Value

Unit

Min Typ. Max

OSC

Frequency of Operation

= 4.5V f external

f internal

8.664

4.332

MHz

ILCH

Halt Mode Recovery Startup Time

Crystal Resonator 20 ms

External RESET Input pulse Width

1.5 t

CYC

PORL

Power Reset Duration 4096 t

CYC

DOGL

Watchdog RESET Output Pulse Width

200 ns

DOG

Watchdog Time-out 12,288 786,432 t

CYC

ILIL

Interrupt Pulse Period (1) t

CYC

OXOV

Crystal Oscillator Start-up Time

50 ms

DDR

Power up rise time VDDmin 100 ms

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CONTROL TIMING(Cont’d)

SERIAL PERIPHERAL INTERFACE

Symbol Ref. Characteristics

OSC

= 8.0MHz

Unit

Min. Max.

Operating Frequency =f

OSC/2=fOP

fOP(m) Master dc 0.5 f

fOP(s) Slave dc 4.0 MHz

1 Cycle Time

CYC(m)

Master 2.0 t

CYC

CYC(s)

Slave 240 ns

2 Enable Lead Time ns

lead(m)

Master (1)

lead(s)

Slave 120

3 Enable Lag time ns

Master (1) Slave 120

4 Clock (SCK)High Time

W(SCKH)

Master 100 ns

W(SCKH)

Slave 90 ns

5 Clock (SCK) Low Time

W(SCKL)

Master 100 ns

W(SCKL)

Slave 90 ns

6 Data Set-up Time

SU(m)

Master 100 ns

SU(s)

Slave 100 ns

7 Data Hold Time (Inputs)

H(m)

Master 100 ns

H(s)

Slave 100 ns

8 Access Time (Time to Data Active fromHigh Impedance State) ns

Slave 0 120

DIS

9 Disable Time (Hold Time to High Impedance State) ns

Slave 240

10 Data Valid

V(m)

Master (Before Capture Edge) 0.25 t

CYC(m)

V(s)

Slave (After Enable Edge)

(2)

120 ns

11 Data Hold Time (Outputs)

HO(m)

Master (Before Capture Edge) 0.25 t

CYC(m)

HO(s)

Slave (After Enable Edge) 0 ns

12 Rise Time (20% V

to 70% VDD,CL= 200pF)

SPI Outputs (SCK, MOSI, MISO) 100 ns

SPI Inputs (SCK, MOSI, MISO, SS) 2.0 µs

13 Fall Time (70% V

to 20% VDD,C

SPI Outputs (SCK, MOSI, MISO) 100 ns

SPI Inputs (SCK, MOSI, MISO, SS) 2.0 µs

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ST7285C

CONTROL TIMING(Cont’d) Figure 36. SPI Master Timing Diagram CPOL=0, CPHA=1

Note: Measurement points are VOL,VOH,VILandV

Figure 37. SPI Master Timing Diagram CPOL=1, CPHA+1

Note: Measurement points are VOL,VOH,VILandV

10 11

1213

(Input)

SCK

(Output)

MISO

MOSI

(Input)

(Output)

VR000107

D7-In D6-In D0-In

D7-Out D6-Out

D0-Out

10 11

12 13

(Input)

SCK

(Output)

MISO

MOSI

(Input)

(Output)

VR000108

D7-Out D6-Out D0-Out

D7-In D6-In

D0-In

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ST7285C

CONTROL TIMING(Cont’d) Figure 38. SPI Master Timing Diagram CPOL=0, CPHA=0

Note: Measurement points are VOL,VOH,VILandV

Figure 39. SPI Master Timing Diagram CPOL=1, CPHA=1

Note: Measurement points are VOL,VOH,VILand V

10 11

1213

(Input)

SCK

(Output)

MISO

MOSI

(Input)

(Output)

VR000109

D7-Out D6-Out D0-Out

D7-In D6-In

D0-In

10 11

1213

(Input)

SCK

(Output)

MISO

MOSI

(Input)

(Output)

VR000110

D7-Out D6-Out D0-Out

D7-In D6-In

D0-In

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ST7285C

CONTROL TIMING(Cont’d) Figure 40. SPI Slave Timing Diagram CPOL=0, CPHA=1

Note: Measurement points are VOL,VOH,VILand V

Figure 41. SPI Slave Timing Diagram CPOL=1, CPHA=1

Note: Measurement points are VOL,VOH,VILand V

10 11

(Input)

SCK

MISO

MOSI

(Input)

(Output)

(Input)

High-Z

VR000111

D7-Out

D6-Out D0-Out

D7-In

D6-In D0-In

10 11

(Input)

SCK

MISO

MOSI

(Input)

(Output)

(Input)

High-Z

VR000112

D7-Out

D6-Out

D0-Out

D7-In

D6-In D0-In

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ST7285C

CONTROL TIMING(Cont’d) Figure 42. SPI Slave Timing Diagram CPOL=0, CPHA=0

Figure 43. SPI Slave Timing Diagram CPOL=1, CPHA=0

(Input)

SCK

MISO

MOSI

(Input)

(Output)

(Input)

High-Z

VR000113

D7-In

D6-In D0-In

D7-Out

D6-Out D0-Out

10 11

(Input)

SCK

MISO

MOSI

(Input)

(Output)

(Input)

High-Z

VR000114

D7-In

D6-In D0-In

D7-Out

D6-Out D0-Out

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ST7285C

CONTROL TIMING(Cont’d)

1. The device must internally provide a hold time of at least 300 ns for the SDA signal in order to bridge the undefined region of the falling edge of SCL

2. The maximum hold time of the START condition only has to be met if the interface does not stretch the

low period of SCL signal

Cb = total capacitance of one bus line in pF

Figure 44. Definition of Timing Terminology

I2C BUS INTERFACE

Parameter

Standard I

C Fast I2C

Symbol Unit

Min Max Min Max

Bus free time between a STOP and START condition

4.7 1.3 Tubs ms

Hold time START condition. After this period,

the first clock pulse is generated

4.0 0.6 Thd:sta µs

LOW period of the SCL clock 4.7 1.3 Tlow µs HIGH period of the SCL clock 4.0 0.6 Thigh µs Set-up time for a repeated START condition 4.7 0.6 Tsu:sta µs Data hold time 0 (1) 0 (1) 0.9(2) Thd:dat µs Data set-up time 250 100 Tsu:dat ns Rise time of both SDA and SCL signals 1000 20+0.1Cb 300 Tr ns Fall time of both SDA and SCL signals 300 20+0.1Cb 300 Tf ns Set-up time for STOP condition 4.0 0.6 Tsu:sto ns Capacitive load for each bus line 400 400 Cb pF

Tbuf

Tlow

Thd:sta

Tsp

Thd:sta Thigh

Thd:dat

Tsu:dat

Tsu:sta

Tsu:sto

SDA

SCL

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ST7285C

7 GENERAL INFORMATION

7.1 PACKAGE MECHANICAL DATA

Figure 45. 80-Pin Plastic Quad Flat Package

Table 14. Ordering Information Table

NOTE: FOR THIS DEVICE, SGS-THOMSON CAN ONLY RECEIVE MOTOROLA S19 FORMAT FOR

ROM CODES.

PQFP080

Dim

mm inches

Min Typ Max Min Typ Max

A 3.40 0.134

0.25 0.010

A2 2.55 2.80 3.05 0.100 0.110 0.120

B 0.30 0.45 0.012 0.018 C

0.13 0.23 0.005 0.009

D 22.95 23.20 23.45 0.904 0.913 0.923

D1 19.90 20.00 20.10 0.783 0.787 0.791 D3

18.40 0.724

E 16.95 17.20 17.45 0.667 0.677 0.687 E1 13.90 14.00 14.10 0.547 0.551 0.555 E3 12.00 0.472

e 0.80 0.031

0° 7°

L 0.65 0.80 0.95 0.026 0.031 0.037

L1 1.60 0.063

Number of Pins

N80 ND24NE16

Sales Types ROM Size RAM Size Temperature Range Package

ST7285A5CQ5 48K 3K -20 to +70°C QFP80 ST7285A5CQ6 48K 3K -40 to +85°C QFP80 ST7285A5CQ8 48K 3K -25 to +85°C QFP80

Page 97

November 1997 97/117

Rev. 1.0

ST72E85

ST72T85

8-BIT MCU FOR RDS WITH 48K EPROM/OTP, 3K RAM,

ADC, TWO TIMERS, SPI, I

C AND SCI INTERFACES

■

4.5V to 5.5V Supply Operating Range

■ Operation at 8.664MHz Oscillator Frequency

for RDS compatibility

■

Fully Static operation

■

-40°Cto+85°C Maximum Operating Temperature Range

■

Run, Wait, Slow, Halt, and RAM Retention modes

■

User EPROM/OTP: 48 Kbytes

■ Data RAM: 3 Kbytes, including 128 byte stack

■

80 pin plastic package

■

62 multifunctional bidirectional I/O lines: – Programmable Interrupt inputs on some I/Os – 8 Analog inputs – EMI Filtering

■

Two 16-bit Timers, each featuring: – 2 Input Captures – 2 Output Compares – External Clock input (on Timer A) – PWM and Pulse Generator modes

■ RDS Radio Data System Filter, Demodulator

and GBS circuits

■

8-bit Analog-to-Digital converter with 8 channel

analog multiplexer

■ Digital Watchdog

■

Dual SPI Serial Peripheral Interface

■

SCI Serial Communications Interface

■ Full I

C multiple Master/Slave interface

■ 2KHz Beep signal generator

■

Master Reset and Power-On Reset

■

8-bit Data Manipulation

■ 63 Basic Instructions

■

17 main Addressing Modes

■

8 x 8 Unsigned Multiply Instruction

■ True Bit Manipulation

■ Complete Development Support on PC/DOS/

WindowsTMReal-Time Emulator

■

Full Software Package (C-Compiler, Cross-

Assembler, Debugger)

CQFP80-W

PQFP80

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ST72E85 ST72T85

1 GENERAL DESCRIPTION

1.1 INTRODUCTION

The ST72E85 is the EPROM version of the ST7285C. Please refer to the ST7285C ROM device Datasheet for further details.

From the User’s point of view, both theST72E85 and the

ST7285C

possess the same software and

hardware features. An additional mode is available to allow program-

ming of the EPROM user memory array.

This is

set by a specific voltage source applied to the VPP/ Test pin.

The

ST72E85

(EPROM) features a 48K EPROM

memory. Watchdog activation is available by Software for

Eprom and OTP devices.

Figure 1. ST72E85 Block Diagram

*Note: EPROM and OTP versions only.

Power on Reset

PA0 - PA7

Pin 65..72

PB0 - PB7

Pin 73..80

OSCin

OSCout

RESET

/ TEST

OSC

8 -BIT CORE

ALU

VR01735P

Internal CLOCK

ADDRESSand DATA BUS

TimerA

PORT A

PORT B

A/D Converter

SPI B

PORT C

PC0 - PC7

Pin 5..12

SPI A

PORT D

SCI

RAM

RDS

FILTER,DEMOD,GBS

TimerB

PD0 - PD7

Pin 13..20

PORT E

PE0 - PE7

Pin 25..32

PORT F

PF0 - PF7 Pin 33..40

PORT H

PORT G

PH0 - PH5

Pin 53..58

PG0 - PG7

Pin 45..52

ROMor EPROM*

48k

Watchdog

RDScomp

MPX

RDS fil RDS ref

ARS AINT

DDPVSSPVDDAVSSA

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ST72E85 ST72T85

1.2 PIN DESCRIPTION

All I/Os from Port A to Port D, as well as PH0, 1 and 2, feature alternate function compatibility. Software selectable input pull-ups are available on

ports featuring interrupt capability (PC4, PC5, PD4, PD5, PF0-PF3, PG3).

VSSA VDDA MPX RDSREF RDSFIL RDSCOMP PH5 PH4 PH3 PH2/RDSDATA PH1/RDSCLKOUT PH0/RDSQUAL PG7 PG6 PG5 PG4 PG3 PG2 PG1 PG0 ARS AINT VDDP VSSP

VSSP VDDP OSCOUT OSCIN PC0/MISO_B PC1/MOSI_B PC2/SCK_B PC3/SS_B PC4/OC2_B PC5/OC1_B PC6/IC2_B PC7/IC1_B PD0/MISO_A PD1/MOSI_A PD2/SCK_A PD3/SS_A PD4 PD5 PD6/SCL PD7/SDA RESET VPP*/TEST VDD VSS

1 2 3 4 5 6 7 8 9 (I10) 10 (I10) 11 12 13 14 15 16 17 (I9) 18 (I9) 19 20 21 22 23 24

64 63

62 61 60 59 58 57 56 55 54 53 52 51 50 49

(I1) 48

47 46 45 44 43 42

80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65

25 26 27 28 29 30 31 32 37 38 39 40

PB7/BEEP/

CLKOUT

PB6/CLKEXT

PB5/OC2_A

PB4/OC1_A

PB3/IC2_A

PB2/IC1_A

PB1/RDI

PB0/TDO

PA7/AIN7

PA6/AIN6

PA5/AIN5

PA4/AIN4

PA3/AIN3

PA2/AIN2

PA1/AIN1

PA0/AIN0

PE0

PE1

PE2

PE3

PE4

PE5

PE6

PE7

PF0

PF1

PF2

PF3

PF4

PF5

PF6

PF7

33 34 35 36

*) On EPROM/OTPversions only

(I2)(I2)(I2)(I2)

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ST72E85 ST72T85

Pin Pin Name(s) Basic Function Alternate Function Remarks

SSP

Ground for Output Buffers

This pin is connected to pin 41

DDP

Power Supply for Output Buffers

This pin is connected to pin 42

3 OSCOUT Oscillator Output pin. 4 OSCIN Oscillator Input pin.

5 PC0/MISO_B I/O Port PC0

SPI B master in/slave out data input/output

Alternate function or I/O. The I/O configuration issoftware selectable as triggered input or push pull output.

6 PC1/MOSI_B I/O Port PC1

SPI B Master Out/ Slave In Data Input/

Output 7 PC2/SCK_B I/O Port PC2 SPI B Serial Clock 8 PC3/SS_B I/O Port PC3 SPI B Slave Select

9 PC4/OC2_B I/O Port PC4

Output Compare 2

on Timer B

Alternate function or I/O. Software selectable as triggered input, push pull output, or triggered interrupt input with pull up (Interrupt I10).

10 PC5/OC1_B I/O Port PC5

Output Compare 1

on Timer B

11 PC6/IC2_B I/O Port PC6

Input Capture 2

on Timer B

Alternate function or I/O. The I/O configuration issoftware selectable as triggered input or push pull output.

12 PC7/IC1_B I/O Port PC7

Input Capture 1

on Timer B.

13 PD0/MISO_A I/O Port PD0

SPI A Master In/

Slave Out Data Input/

Output

14 PD1/MOSI_A I/O Port PD1

SPI A Master Out/

Slave In data Input/

Output

15 PD2/SCK_A I/O Port PD2 SPI A Serial Clock 16 PD3/SS_A I/O Port PD3 SPI A Slave Select 17 PD4 I/O PortPD4 - Software selectable as triggered input, push

pull output, open drain output or triggered interrupt input with pull up (Interrupt I9).

18 PD5 I/O PortPD5 19 PD6/SCL I/O Port PD6 I

C Serial Clock Alternate function or I/O. The I/O configuration

is software selectable as triggered input or open drain output.

20 PD7/SDA I/O Port PD7 I

C Serial Data

21 RESET General Reset -

Bidirectional. An active low signal forces MCU initialization. This event is the top priority nonmaskable interrupt. Asan output, it can be used to reset external peripherals.

22 V

/TEST RESERVED -

Input. This pin MUSTbe tieddirectly to V

during normal operation. In Programming Mode, this pin is connected to V

23 V

Power Supply for all logic circuitry

Except for output buffers and pull-ups.

24 V

Ground for all logic circuitry

Datasheet ST72T85A5Q6, ST72E85A5G0, ST7285C, ST7285A5CQ8, ST7285A5CQ6 Datasheet (SGS Thomson Microelectronics)

Specifications and Main Features

Frequently Asked Questions

User Manual