SGS Thomson Microelectronics ST72F264G2M6, ST72F264G2B6, ST72264G2M6, ST72264G2B6, ST72264G2 Datasheet

ST72260G, ST72262G,

ST72264G

8-BIT MCU WITH FLASH OR ROM MEM ORY,

ADC, TWO 16-BIT TIMERS, I

■ Memories

– 4 K or 8 Kby tes Program memory: ROM or

Single voltage extended Flash (XFlash) with
read-out protection write protection and In­Circuit Programming and In-Application Pro­gramming (ICP and IAP). 10K write/erase cy­cles guaranteed, data retention: 20 years at
55°C.

– 256 bytes RAM

■ Clock, Re set and Supp ly Managem ent

– Enhanced reset system
– Enhanced low voltage supply supervisor

(LVD) with 3 programmable levels and auxil­iary voltage detector (AVD) with interrupt ca­pability for implementing safe power-down
procedures

– Clock sources: crystal/ceramic resonat or os-

cillators , internal RC os cillator, clock se curity

system and bypass for external clock
– PLL for 2x frequency multiplication
– Clock-out capability
– 4 Power Saving Modes: Halt, Active Halt,Wait

and Slow

■ Interrupt Management

– Nested interrupt controller
– 10 interrupt vectors plus TRAP and RESET
– 22 external interrupt lines (on 2 vectors)

■ 22 I/ O P o rts

– 22 multifunctional bidirectional I/O lines
– 20 alternate function lines
– 8 high sink outputs

■ 4 Timers

– Main Clock Controller with Real time base and

Clock-out capabilities
– Configurable watchdog timer

Device Summary

Features

Program memory - bytes 4K 4K 8K 4K 8K
RAM (stack) - bytes 256 (128)

Periphe rals

Operating Supply 2.4 V to 5.5 V
CPU Frequency Up to 8 MHz (with oscillator up to 16 MHz) PLL 4/8 Mhz
Operating Temperature -40° C to +85° C 0° C to +70° C
Packages SO28 / SDIP32 LFBGA

ST72260G1 ST72262G1 ST72262G2 ST72264G1 ST72264G2

Watchdog timer,

RTC,

Two16-bit timers,

SPI

Watchdog timer, RTC

Two 16-bit timers,

SPI, ADC

2

C, SPI, SCI INTERFACES

SDIP32

LFBGA 6x6mm

SO28

– Two 16-bit timers with: 2 input captures, 2 out-

put compares, external clock input on one tim­er, PWM and Pulse generator modes

■ 3 Communications Interfaces

– SPI synchronous serial interface

2

C multimaster interface

–I
– SCI asynchronous serial interface (LIN com-

patible)

■ 1 Analog peripheral

– 10-bit ADC with 6 input channels

■ Instruction Set

– 8-bit data manipulation
– 63 basic instructions
– 17 main addressing modes
– 8 x 8 unsigned multiply instruction

■ Development Tools

– Full hardware/software development package

Watchdog timer, RT C

Two 16-bit timers ,

SPI, SCI, I

2

C, ADC

Rev. 1.7

August 2003 1/171

1

Table of Contents

ST72260G, ST72262G,

ST7226 4G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 PIN DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 REGISTER & MEMORY MAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4 FLASH PROGRAM MEMORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.2 MAIN FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.3 PROGRAMMING MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.4 ICC INTERFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.5 MEMORY PROTECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.6 REGISTER DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5 CENTRAL PROCESSING UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.2 MAIN FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.3 CPU REGISTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6 SUPPLY, RESET AND CLOCK MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6.1 PHASE LOCKED LOOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6.2 MULTI-OSCILLATOR (MO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3 RESET SEQUENCE MANAGER (RSM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

6.4 SYSTEM INTEGRITY MANAGEMENT (SI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

7 INTERRUPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7.2 MASKING AND PROCESSING FLOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7.3 INTERRUPTS AND LOW POWER MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

7.4 CONCURRENT & NESTED MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

7.5 INTERRUPT REGISTER DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

8 POWER SAVING MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

8.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

8.2 SLOW MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

8.3 WAIT MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

8.4 ACTIVE-HALT AND HALT MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

8.5 HALT MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

9 I/O PORTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

9.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

9.2 FUNCTIONAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

9.3 I/O PORT IMPLEMENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

9.4 UNUSED I/O PINS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

9.5 LOW POWER MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

9.6 INTERRUPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

9.7 DEVICE-SPECIFIC I/O PORT CONFIGURATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

171

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9.8 I/O PORT REGISTER DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

10 MISCELLANEOUS REGISTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

10.1 I/O PORT INTERRUPT SENSITIVITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

10.2 I/O PORT ALTERNATE FUNCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

10.3 MISCELLANEOUS REGISTER DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

11 ON-CHIP PERIPHERALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

11.1 WATCHDOG TIMER (WDG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

11.2 MAIN CLOCK CONTROLLER WITH REAL TIME CLOCK (MCC/RTC) . . . . . . . . . . . . . 53

11.3 16-BIT TIMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

11.4 SERIAL PERIPHERAL INTERFACE (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

11.5 SERIAL COMMUNICATIONS INTERFACE (SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

11.6 I2C BUS INTERFACE (I2C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

11.7 10-BIT A/D CONVERTER (ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

12 INSTRUCTION SET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

12.1 CPU ADDRESSING MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

12.2 INSTRUCTION GROUPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

13 ELECTRICAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

13.1 PARAMETER CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

13.2 ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

13.3 OPERATING CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

13.4 SUPPLY CURRENT CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

13.5 CLOCK AND TIMING CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

13.6 MEMORY CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

13.7 EMC CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

13.8 I/O PORT PIN CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

13.9 CONTROL PIN CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

13.10 TIMER PERIPHERAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

13.11 COMMUNICATION INTERFACE CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . 149

13.12 10-BIT ADC CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

14 PACKAGE CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

14.1 PACKAGE MECHANICAL DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

14.2 THERMAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

14.3 SOLDERING AND GLUEABILITY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

15 DEVICE CONFIGURATION AND ORDERING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . 157

15.1 OPTION BYTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

15.2 DEVICE ORDERING INFORMATION AND TRANSFER OF CUSTOMER CODE . . . . 159

15.3 DEVELOPMENT TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

15.4 ST7 APPLICATION NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

16 SUMMARY OF CHANGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

ERRATA SHEET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

3

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ST72260G, ST72262G, ST72264G

17 SILICON IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

18 REFERENCE SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

19 SILICON LIMITATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

19.1 EXECUTION OF BTJX INSTRUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

19.2 I/O PORT B AND C CONFIGURATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

19.3 16-BIT TIMER PWM MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

19.4 SPI MULTIMASTER MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

19.5 MINIMUM OPERATING VOLTAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

19.6 CSS FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

19.7 INTERNAL AND EXTERNAL RC OSCILLATOR WITH LVD . . . . . . . . . . . . . . . . . . . . 167

19.8 EXTERNAL CLOCK WITH PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

19.9 HALT MODE POWER CONSUMPTION WITH ADC ON . . . . . . . . . . . . . . . . . . . . . . . 168

19.10 ACTIVE HALT WAKE-UP BY EXTERNAL INTERRUPT . . . . . . . . . . . . . . . . . . . . . . . 168

19.11 A/D CONVERTER ACCURACY FOR FIRST CONVERSION . . . . . . . . . . . . . . . . . . . . 168

19.12 NEGATIVE INJECTION IMPACT ON ADC ACCURACY . . . . . . . . . . . . . . . . . . . . . . . 168

19.13 ADC CONVERSION SPURIOUS RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

19.14 FUNCTIONAL EMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

20 DEVICE MARKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

21 ERRATA SHEET REVISION HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

To obtain the most recent version of this datasheet,

please check at www.st.com>products>technical literature>datasheet
Please note that an errata sheet can be found at the end of this document on page 166.

4/171

1 INTRODUCTION

ST72260G, ST72262G, ST72264G

The ST72260G, ST72262G and ST72264G devic­es are members of the ST7 microcontroller family.
They can be grouped as follows :

– ST72264G devices are designed for mid-range

applications with ADC, I

2

C and SCI interface ca-

pabilities.

– ST72262G devices target the same range of ap-

plications but without I

– ST72260G devices are for applications that do

not need ADC, I

2

C interface or SCI.

2

C peripherals or SCI.

All devices are based on a common industry­standard 8-bit core, featuring an enhanced instruc­tion set.

The ST72F260G, ST72F262G, and ST72F264G
versions feature single-voltage FLASH memory

Figure 1. General Block D iagram

Internal

OSC1
OSC2

V

V

RESET

DD

SS

MULTI OSC

+

CLOCK F ILTE R

MCC/RTC

LVD

POWER
SUPPLY

CONTROL

8-BIT CO RE

ALU

CLOCK

with byte-by-byte In-Circuit Programming (ICP)
capabilities.

Under software control, all devices can be placed
in WAIT, SLOW, Ac tive-HALT or H ALT mode, re­ducing power consumption when the application is
in idle or stand-by state.

The enhanced instruction set and addressing
modes of the ST7 offer both power and flexibility to
software developers, enabling the design of highly
efficient and compact application code. In addition
to standard 8-bit data management, all ST7 micro­controllers feature true bit manipulation, 8x8 un­signed multiplication and indirect addressing
modes.

For easy reference, all parametric data is locat ed
in Section 13 on page 122.

I2C*

SCI*

PA7:0

PORT A

ICD

ADDRESS AND DATA BUS

SPI

PORT B

16-BIT TIMER A

(8 bits)

PB7:0

(8 bits)

PROGRAM

MEMORY

(4 or 8K Bytes)

RAM

(256 Bytes)

*Not avai l abl e on some de vices, see devi ce summar y on page 1.

PORT C

10-BIT ADC*

16-BIT TIMER B

WATCHDOG

PC5:0

(6 bits)

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ST72260G, ST72262G, ST72264G

2 PIN DESCRI PTION

Figure 2. 28-Pin SO Package Pinout

RESET

OSC1
OSC2

SS

/PB7

SCK/PB6
MISO/PB5
MOSI/PB4

OCMP2_A/PB3

ICAP2_A/PB2

OCMP1_A/PB1

ICAP1_A/PB0

AIN5/EXTCLK_A/PC5

2

/OCMP2_B/PC4

AIN4

2

AIN3

/ICAP2_B/PC3

1

Configur abl e by optio n byte

2

Alternate function not available on S T 72260

3

Alternate function not available on S T 72260 and ST72262

Figure 3. 32-Pin SDIP Package Pinout

RESET

OSC1
OSC2

SS

/PB7

SCK/PB6
MISO/PB5
MOSI/PB4

NC
NC

OCMP2_A/PB3

ICAP2_A/PB2

OCMP1_A/PB1

ICAP1_A/PB0

AIN52/EXTCLK_A/PC5

2

/OCMP2_B/PC4

AIN4

2

/ICAP2_B/PC3

AIN3

1

Confi gu rable by option byte

2

Alternate function not available on ST72260

3

Alternate function not available on ST72260 and ST72262

1
2
3
4
5
6
7
8
9
10
11
12
13

14

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

ei1 ei0

ei0 or ei1

ei1

ei0

ei0

ei1

ei0 or ei1

V

28

DD

V

27

SS

ICCSEL

26

(HS)/ICCCLK

PA0

25

(HS)/ICCDATA

PA1

24

PA2

23
22
21
20
19
18
17

1

16
15

32
31
30
29
28
27
26
25
24
23
22
21
20
19

1

18
17

(HS)
PA3 (HS)
PA4 (HS)/SCLI
PA5(HS)/RDI
PA6 (HS)/SDAI
PA7 (HS)/TDO
PC0/ICAP1_B/AIN0
PC1/OCMP1_B/AIN1
PC2/MCO/AIN2

(HS) 20mA high sink capability
eiX associated external interrupt vector

V

DD

V

SS

3

3

3

3

2

2

2

ICCSEL
PA0 (HS)/ICCCLK
PA1 (HS)/ICCDATA
PA2 (HS)
PA3 (HS)
NC

NC

PA4 (HS)/SCLI
PA5 (HS)/RDI
PA6 (HSI/SDAI

PA7 (HS)/TDO
PC0/ICAP1_B/A IN0
PC1/OCMP1_B /AIN1

PC2/MCO/AIN2

(HS) 20mA high sink capability
eiX associated external interrupt vector

3

3

3

3

2

2

2

6/171

Figure 4. TFBGA Package Pinout (view through package)

123456

A

B

C

D

E

F

ST72260G, ST72262G, ST72264G

7/171

ST72260G, ST72262G, ST72264G

PIN DESCRIPTION (Cont’d)

For external pin connection guidelines, refer to Section 13 "ELECTRICAL CHARACTERISTICS" on page

122.

Legend / Abbreviations for Table 1:

Type: I = input, O = output, S = supply
Input level: A = Dedicated analog input
In/Output lev e l: C
Output level: HS = 20 mA high sink (on N-buffer only)
Port and control configuration:

– Input: float = floating, wpu = weak pull-up, int = interrupt

– Output: OD = open drain
Refer to Section 9 "I/O PORTS" on page 38 for more details on the software configuration of the I/O ports.
The RESET confi g ur at ion of each pin is sho wn in b o ld. This configura ti o n is valid as long as t h e device is

in reset state.

Table 1. Device Pin Description

= CMOS 0.3 VDD/0.7 VDD with input trigger

T

2)

, PP = push-pull

1)

, ana = analog

Pin n°

Level Port / Control

Pin Name

Type

BGA

SO28

SDIP32

1 1 A3 RESET I/O C

2 2 C4 OSC1

3 3 B3 OSC2
4 4 A2 PB7/SS

3)

3)

I/O C

T

I

O

5 5 A1 PB6/SCK I/O C
6 6 B1 PB5/MISO I/O C
7 7 B2 PB4/MOSI I/O C
8 C1 NC

D1 NC
10 8 C3 PB3/OCMP2_A I/O C
11 9 D2 PB2/ICAP2_A I/O C
12 10 E1 PB1 /OCMP1_A I/O C
13 11 F1 PB0 /ICAP1_A I/O C

14 12 F2 PC5/EXTCLK_A/AIN5 I/O C

15 13 E2 PC4/OCMP2_B/AIN4 I/O C

16 14 F3 PC3/ ICAP2_B/AIN3 I/O C

Input

Main

OD

Function

(after

reset)

PP

Alternate Function

Top priority non maskable interrupt (ac­tive low)

Input Output

Output

float

wpu

int

XX

ana

External clock input or Resonator oscilla­tor inverter input or resistor input for RC
oscillator

Resonator oscillator inverter output or ca­pacitor input for RC oscillator

X ei1 X X Port B7 SPI Slave Select (active low)

T

X ei1 X X Port B6 SPI Serial Clock

T

X ei1 X X Port B5 SPI Master In/ Slave Out Data

T

X ei1 X X Port B4 SPI Master Out / Slave In Data

T

Not Connected9 C2 NC

X ei1 X X Port B3 Timer A Output Compare 2

T

X ei1 X X Port B2 Timer A Input Capture 2

T

X ei1 X X Port B1 Timer A Output Compare 1

T

X ei1 X X Port B0 Timer A Input Capture 1

T

X ei0/ei1 X X X Port C5

T

X ei0/ei1 X X X Port C4

T

X ei0/ei1 X X X Port C3

T

Timer A Input Clock or ADC
Analog Input 5

Timer B Output Compare 2 or
ADC Analog Input 4

Timer B Input Capture 2 or
ADC Analog Input 3

8/171

ST72260G, ST72262G, ST72264G

Pin n°

SDIP32

SO28

Pin Name

BGA

Level Port / Control

Type

17 15 E3 PC2/MCO/AIN2 I/O C

18 16 F4 PC1/OCMP1_B/AIN1 I/O C

19 17 D3 PC0/ICAP1_B/AIN0 I/O C
20 18 E4 PA7/TDO I/O C

21 19 F5 PA6/SDAI I/O C
22 20 F6 PA5 /RDI I/O C
23 21 E6 PA4/SCLI I/O C

T
T
T
T

24 E5 NC

D5 N C
26 22 C6 PA3 I/O C
27 23 D4 PA2 I/O C

T
T

C5 NC

B6 NC
28 24 A6 PA1/ICCDATA I/O C

29 25 A5 PA0/ICCCLK I/O C
30 26 B5 ICCSEL I C

31 27 A4 V
32 28 B4 V

SS
DD

T

T

T

S Ground
S Main power supply

Main

Input

Input Output

Output

float

X ei0/ei1 X X X Port C2

T

X ei0/ei1 X X X Port C1

T

X ei0/ei1 X X X Port C0

T

wpu

int

ana

OD

Function

(after

reset)

PP

Alternate Function

Main clock output (f

CPU

) or

ADC Analog Input 2
Timer B Output Compare 1 or

ADC Analog Input 1
Timer B Input Capture 1 or

ADC Analog Input 0

HS X ei0 X X Port A7 SCI output
HS X ei0 T Port A6 I2C DATA
HS X ei0 X X Port A5 SCI input
HS X ei0 T Port A4 I2C CLOCK

Not Connected25 D6 NC

HS X ei0 X X Port A3
HS X ei0 X X Port A2

Not Connected

HS X ei0 X X Port A1 In Circuit Communication Data
HS X ei0 X X Port A0

In Circuit Communication
Clock

X ICC mode pin, must be tied low

Notes:

1. In the interrupt input column, “eiX ” define s the asso ciated exte rnal interrupt vec tor. If the weak pul l-up
column (wpu) is merged with the interrupt column (int), then the I/O configuration is a pull-up interrupt in­put, otherwise the configuration is a floating interrupt input. Port C is mapped to ei0 or ei1 by option byte.

2. In the open drain output column, “T” defines a true open drain I/O (P-Buffer and protection diode to V
are not implemented). See Section 9 "I/O PORTS" on page 38 for more details.

DD

3. OSC1 and OSC2 pins connect a crystal or ceramic resonator, an external RC, or an external source to
the on-chip oscillator see S ection 2 "PIN DESCRIPTION" on page 6 and Section 6.2 "MULTI-OSC ILLA-

TOR (MO)" on page 21 for more details.

9/171

ST72260G, ST72262G, ST72264G

3 REGISTER & MEMORY MAP

As sho wn in Figure 5, the MCU is capable of ad-
dressing 64K bytes of memories and I/O registers.

The available memory locations consist of 128
bytes of register location, 256 bytes of RAM and
up to 8 Kbytes of user program memory. The RAM
space includes up to 128 bytes for the sta ck from
0100h to 017Fh.

The highest address b ytes contain the user reset
and interrupt vectors.

The Flash memory c on tains tw o sectors (s ee Fig-

ure 5) mapped i n the upper part of the ST7 ad-

Figure 5. Me m ory Map

0000h

007Fh
0080h

017Fh

0180h

HW Registers

(see Table 2)

RAM

(256 Bytes)

Reserved

dressing space so the reset and interrupt vectors
are located in Sector 0 (F000h-FFFFh).

The size of Flash Sector 0 and other device op­tions are configurable by Option byte (refer to Sec-

tion 15.1 on page 157).

IMPORTANT: Memory locations marked as “Re­served” must neve r be ac cess ed. A cce ssing a re­seved area c an have unpredictable effects on t he
device.

0080h

00FFh
0100h

017Fh

Short Addressing RAM

Zero page

(128 Bytes)

Stack or

16-bit Addressing RAM

(128 Bytes)

8K FLASH

PROGRAM MEMORY

10/171

DFFFh

E000h

FFDFh

FFE0h

FFFFh

Program Memory

(4K, 8 KBytes)

Interrupt & Reset Vectors

(see Table 5 on page 32)

E000h

EFFFh

F000h

FFFFh

4 Kbytes

SECTOR 1

4 Kbytes

SECTOR 0

Table 2. Hardware Register Map

ST72260G, ST72262G, ST72264G

Address Block

0000h
0001h

Port C

0002h

Register

Label

PCDR
PCDDR
PCOR

Register Name

Port C Data Register
Port C Data Direction Register

Port C Option Register
0003h Reserved (1 Byte)
0004h

0005h
0006h

Port B

PBDR
PBDDR
PBOR

Port B Data Register

Port B Data Direction Register

Port B Option Register
0007h Reserved (1 Byte)

0008h
0009h
000Ah

Port A

PADR
PADDR
PAOR

Port A Data Register

Port A Data Direction Register

Port A Option Register
000Bh

to

Reserved (17 Bytes)

001Bh
001Ch

001Dh
001Eh
001Fh

ITC

ISPR0
ISPR1
ISPR2
ISPR3

Interrupt software priority register0

Interrupt software priority register1

Interrupt software priority register2

Interrupt software priority register3

Reset

Status

xx000000h

00h
00h

1)

00h

00h
00h

1)

00h

00h
00h

FFh
FFh
FFh
FFh

1)

Remarks

2)

R/W

2)

R/W

2)

R/W

R/W
R/W
R/W.

R/W
R/W

R/W

R/W
R/W
R/W

R/W
0020h MISCR1 Miscellanous register 1 00h R/W
0021h

0022h
0023h

SPI

SPIDR
SPICR
SPICSR

SPI Data I/O Register
SPI Control Register
SPI Status Register

xxh
0xh
00h

R/W

R/W

R/W
0024h WATCHDOG WDGCR Watchdog Control Register 7Fh R/W

0025h SICSR System Integrity Control / Status Register 000x 000x R/W
0026h MCC MCCSR Main Clock Control / Status Register 00h R/W
0027h Reserved (1 Byte)

2

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

002Fh
0030h

I2CCR
I2CSR1

2

C

I

I2CSR2
I2CCCR
I2COAR1
I2COAR2
I2CDR

I

C Control Register

2

I

C Status Register 1

2

I

C Status Register 2

2

I

C Clock Control Register

2

I

C Own Address Register 1

2

I

C Own Address Register2

2

I

C Data Register

00h
00h
00h
00h
00h
40h
00h

Reserved (2 Bytes)

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

11/171

ST72260G, ST72262G, ST72264G

Address Block

0031h
0032h
0033h
0034h
0035h
0036h
0037h
0038h

TIMER A
0039h
003Ah
003Bh
003Ch
003Dh
003Eh
003Fh

Register

Label

TACR2
TACR1
TASCSR
TAIC1HR
TAIC1LR
TAOC1HR
TAOC1LR
TACHR
TACLR
TAACHR
TAACLR
TAIC2HR
TAIC2LR
TAOC2HR
TAOC2LR

Register Name

Timer A Control Register 2
Timer A Control Register 1
Timer A Control/Status Register
Timer A Input Capture 1 High Register
Timer A Input Capture 1 Low Register
Timer A Output Compare 1 High Register
Timer A Output Compare 1 Low Register
Timer A Counter High Register
Timer A Counter Low Register
Timer A Alternate Counter High Register
Timer A Alternate Counter Low Register
Timer A Input Capture 2 High Register
Timer A Input Capture 2 Low Register
Timer A Output Compare 2 High Register
Timer A Output Compare 2 Low Register

Reset

Status

00h
00h
xxh
xxh
xxh
80h
00h

FFh
FCh
FFh
FCh

xxh

xxh

80h

00h

0040h MISCR2 Miscellanous register 2 00h R/W
0041h

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

TIMER B

TBCR2
TBCR1
TBSCSR
TBIC1HR
TBIC1LR
TBOC1HR
TBOC1LR
TBCHR
TBCLR
TBACHR
TBACLR
TBIC2HR
TBIC2LR
TBOC2HR
TBOC2LR

Timer B Control Register 2
Timer B Control Register 1
Timer B Control/Status Register
Timer B Input Capture 1 High Register
Timer B Input Capture 1 Low Register
Timer B Output Compare 1 High Register
Timer B Output Compare 1 Low Register
Timer B Counter High Register
Timer B Counter Low Register
Timer B Alternate Counter High Register
Timer B Alternate Counter Low Register
Timer B Input Capture 2 High Register
Timer B Input Capture 2 Low Register
Timer B Output Compare 2 High Register
Timer B Output Compare 2 Low Register

00h

00h

xxh

xxh

xxh

80h

00h
FFh
FCh
FFh
FCh

xxh

xxh

80h

00h

Remarks

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

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

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

SCI

SCISR
SCIDR
SCIBRR
SCICR1
SCICR2
SCIERPR
SCIETPR

SCI Status Register
SCI Data Register
SCI Baud Rate Register
SCI Control Register1
SCI Control Register2
SCI Extended Receive Prescaler Register
SCI Extended Transmit Prescaler Register

C0h

xxh

00h

x000 0000h

00h

00h

00h

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

0057h

to

Reserved (24 Bytes)

006Eh
006Fh

0070h
0071h

ADC

ADCDRL
ADCDRH
ADCCSR

Data Register Low
Data Register High
Control/Status Register

3)

3)

00h

00h

00h

Read Only
Read Only

R/W
0072h FLASH FCSR F lash Contr ol Register 00h R/W
0073h

to

Reserved (13 Bytes)

007Fh

12/171

ST72260G, ST72262G, ST72264G

Legend: x=Unde fined, R/W=R e ad/Write
Notes:

1. The contents of the I/O p ort DR registers are readable only i n out put c onf iguration. I n i nput c onf igura­tion, the values of the I/O pins are returned instead of the DR register contents.

2. The bits associated with unavailable pins must always keep their reset value.

3. For compatibility with the ST72C254, the ADCDRL and ADCDRH data registers are located with the
LSB on the lower address (6Fh) and the MSB on the higher address (70h). As this scheme is not little En­dian, the ADC data registers cannot be treated by C programs as an integer, but have to be treated as two
char registers.

13/171

ST72260G, ST72262G, ST72264G

4 FLASH PROGRAM MEMO RY

4.1 In troduction

The ST7 single voltage extended Flash (XFlash) is
a non-volatile memory that can be electrically
erased and programmed either on a by te-by-byte
basis or up to 32 bytes in parallel.

The XFlash devices can be programmed off-board
(plugged in a programming tool) or on-board using
In-Circuit Programming or In-Application Program­ming.

The array matrix organ isation allows each sector
to be erased and reprogrammed wi thout affecting
other sectors.

4.2 Main Features

■ ICP (In-Circuit Programming)

■ IAP (In-Application Programming)

■ ICT (In-Circuit Testing) for downloading and

executing user application test patterns in RAM

■ Sector 0 size configurable by option byte

■ Read-out and write protection against piracy

4.3 PROGRAMMING MODES

The ST7 can be programmed in three different
ways:

– Insertion in a programming tool. In this mode,

FLASH sectors 0 and 1 and op tion byte row
can be programmed or erased.

– In-Circuit Programming. In this mode, FLAS H

sectors 0 and 1 and op tion byte row can be
programmed or erased without removing the
device from the application board.

– In-Application Programming. In this mode,

sector 1 can be programme d or erased with­out removing the device from the application

board and while the application is running.

4.3.1 In-Circuit Programming (ICP)

ICP us es a pr ot o c ol c al l e d I CC ( I n- Ci r c ui t C om mu ­nication) which allows an ST7 plugged on a print­ed circuit board (PCB) to communicate with an ex­ternal programming device connected via cable.
ICP is performed in three steps:

Switch the ST7 to ICC mode (In-Circuit Communi­cations). This is done by driving a specific signal
sequence on the ICCCLK/DATA pins while the
RESET pin is pulled low. When the ST7 enters
ICC mode, it fetches a specific RESET vector
which points to the ST7 System Memory contain­ing the ICC protocol routine. This routine enables
the ST7 to receive bytes from the ICC interface.

– Download ICP Driver cod e in RAM from the

ICCDATA pin

– Execute ICP Driver code in RAM to program

the FLASH memory

Depending on the ICP Driver code downloaded in
RAM, FLASH memo ry programming can be fully
customized (number of bytes to program, program
locations, or selection of the serial communication
interface for downloading).

4.3.2 In Application Programming (IAP)

This mode uses an IAP Driver program previously
programmed in Sector 0 by the user (in ICP
mode).

This mode is fully controlled by user software. This
allows it to be adapted to the user application, (us­er-defined strategy for entering programming
mode, choice of c om mun ications protoc ol used t o
fetch the data to be stored etc.)
IAP mode can be used to program any memory ar­eas except Sector 0, which is write/erase protect­ed to allow recovery in case errors occur during
the programming operation.

14/171

FLASH PROGRAM MEMORY (Cont’d)

ST72260G, ST72262G, ST72264G

4.4 ICC interface

ICP needs a minimum of 4 and u p to 7 pins to be
connected to the programming tool. These pins
are:

– RESET
–V

: device reset

: device power supply ground

SS

– ICCCLK: ICC output serial clock pin
– ICCDATA: ICC input serial data pin
– ICCSEL: ICC selection (not required on devic-

es without ICCSEL pin)

– OSC1: main clock input for external source

(not required on devices without OSC1/OSC2
pins)

: application board power supply (option-

–V

DD

al, see Note 3)

Notes:

1. If the ICCCLK or ICCDATA pins are only use d
as outputs in the application, no sign al iso lation is
necessary. As soon as the Programming Tool is
plugged to the board, even if an ICC session is not
in progress, the ICCCLK and ICCDATA pins are
not available for the application. If they are used as
inputs by the application, isolation such as a serial
resistor has to be implemented in case another de­vice forces the signal. Refer to the Programming

Figure 6. Typical ICC Interface

Tool documentation for recommended resistor val­ues.

2. During the ICP session, the programming tool
must contr o l the RESET

pin. This can lead to con­flicts between the programming tool and the appli­cation reset circuit if it drives more than 5mA at
high level (push pull output or pull-up resistor<1K).
A schottky diode can be u sed to isolate t he appli­cation RESET circuit in this case. When using a
classical RC network with R>1K or a reset man­agement IC with open drain outpu t and pull-up re­sistor>1K, no additional com ponents are needed.
In all cases the user must ensure that no external
reset is generated by the application during the
ICC session.

3. The use of Pin 7 of the ICC connec tor depends
on the Programming Tool architecture. This pin
must be connected when using most ST Program­ming Tools (it is used to monitor the application
power supply). Please refer to the Programming
Tool manual.

4. Pin 9 has to be connected to the OSC1 pin of
the ST7 when the clock is not avai lable in the ap­plication or if the selected clock option is not pro­grammed in the option byte. ST7 devices with mul­ti-oscillator capability need to have OSC2 ground­ed in this case.

APPLICATION
POWER SUPPLY

OPTIONAL
(See Note 3)

C

L2

VDD

OSC2

OPTIONAL
(See Note 4)

C

L1

OSC1

ST7

PROGRAMMING TOOL

ICC CONNECTOR

ICC Ca ble

ICC CONNECTOR

HE10 CONNECTOR TYPE

975 3

10kΩ

VSS

RESET

ICCSEL

ICCCLK

1
246810

ICCDATA

APPL ICATION BOARD

APPLICATION
RESET SOURCE

See Note 2

See Note 1

APPLICATION

I/O

15/171

ST72260G, ST72262G, ST72264G

FLASH PROGRAM MEMORY (Cont’d)

4.5 Memory Protection

There are two different types of memory protec­tion: Read Out Protection and Write/Erase Protec­tion which can be applied individually.

4.5.1 Read out Protection

Read out protection, when selected, makes it im­possible to extract the m emory content from the
microcontroller, thus preventing piracy.

In flash devices, this protection is removed by re­programming the option. In this case the program
memory is automatically erased and the device
can be reprogrammed.

Read-out protection selection depends on the de­vice type:

– In Flash devices it is enabled and removed

through the FMP_R bit in the option byte.

– In ROM devices it is enabled by mask option

specified in the Option List.

4.5.2 Flash Write/Erase Protection

Write/erase protection, when set, makes it impos­sible to both overwrite and erase program memo­ry. Its purpose is to provide advanced security to
applications and prevent a ny change bei ng mad e
to the memory content.

Warning: Once set, Write/erase protection can
never be removed. A write-protected flash device
is no longer reprogrammable.

Write/erase protection is enabled through the
FMP_W bit in the option byte.

4.6 Register Description FLASH CONTROL/STATUS REGISTER (FCSR)

Read/Write
Reset Value: 000 0000 (00h)
1st RASS Key: 0101 0110 (56h)
2nd RASS Key: 1010 1110 (AEh)

70

00000OPTLATPGM

Note: This register is reserved for programming
using ICP, IAP or other program ming methods. It
controls the XFlash p ro grammin g and erasing op­erations. For details on XFlash programming, refer
to the ST7 Flash Programming Reference Manual.

When an EPB or another programming tool is
used (in socket or ICP mode), the RASS k eys are
sent automatically.

16/171

5 CENTRAL PRO CESSING UNIT

ST72260G, ST72262G, ST72264G

5.1 INTRODUCTION

This CPU has a full 8-bit architecture and contains
six internal registers allowing efficient 8-bit data
manipulation.

5.2 MAIN FEATURES

■ Enable executing 63 basic instructions

■ Fast 8-bit by 8-bit multiply

■ 17 main addressing modes (with indirect

addressing mode)

■ Two 8-bit index registers

■ 16-bit stack pointer

■ Low power HALT and WAIT modes

■ Priority maskable hardware interrupts

■ Non-maskable software/hardware interrupts

Figure 7. CPU Registers

5.3 CPU REGISTERS

The 6 CPU registers shown in Figure 7 are not
present in the memory mapping and are accessed
by specifi c ins t r uc tions.

Accumulator (A)

The Accumulator is an 8-bit general purpose reg­ister used to hold operan ds and the results of the
arithmetic and logic calculations and to manipulate
data.

Index Registers (X and Y)

These 8-bit registers are used to create effective
addresses or as tempora ry storage areas f or dat a
manipulation. (The Cross-A ssembler generates a
precede instruction (PRE) to indicate that the fol­lowing instruction refers to the Y register.)

The Y register is not affected by the interrupt auto­matic procedures.

Program Cou nt er (P C )

The program counter is a 16-bit register containing
the address of the next instruction to be executed
by the CPU. It is made of two 8-bit registers PCL
(Program Counter Low which is the LSB) and PCH
(Program Counter High which is the MSB).

70

RESET VALUE = XXh

70

RESET VALUE = XXh

70

RESET VALUE = XXh

15 8

RESET VALUE = RESET VECTOR @ FFFEh-FFFFh

15

RESET VALUE = STACK HIGHER ADDRESS

PCH

RESET VALUE =

7

70
1C1I1HI0NZ

1X11X1XX
70

8

PCL

0

ACCUMULA T OR

X INDEX REGISTER

Y INDEX REGISTER

PROGRAM COUNTER

CONDITION CODE REGISTER

STACK POINTER

X = Undefined Value

17/171

ST72260G, ST72262G, ST72264G

CENTRAL PROCESSING UNIT (Cont’d)
Condition Code Register (CC)

Read/Write
Reset Value: 111x1xxx

70

11I1HI0NZ

C

The 8-bit Condition Code register c ontains the in­terrupt masks and four flags representative of the
result of the instruction just executed. This register
can also be handled by the PUSH and POP in­structions.

These bits can be individually tested and/or con­trolled by specific instructions.

Arithmetic Management Bits

Bit 4 = H

Half carry

.

This bit is set by hardware when a carry occurs be­tween bits 3 and 4 of t he ALU during an ADD or
ADC instructions. It is reset by hardware during
the same instruction s.

0: No half carry has occurred.
1: A half carry has occurred.

This bit is tested using the JRH or JRNH instruc­tion. The H bit is useful in BCD arithmetic subrou­tines .

Bit 2 = N

Negative

.

This bit is set and cleared by hardware. It is repre­sentative of the result sign of the last arithmetic,
logical or data manipulation. I t’s a copy of the re-

th

sult 7

bit.
0: The result of the last operation is positive or null.
1: The result of the last operation is negative

(i.e. the most significant bit is a logic 1).

This bit is accessed by the JRMI and JRPL instruc­tions.

Bit 1 = Z

Zero

.

This bit is set and cleared by hardware. This bit in­dicates that the result of the last arithmetic, logical
or data manipulation is zero.
0: The result of the last operation is different from

zero.

1: The result of the last operation is zero.
This bit is accessed by the JREQ and JRNE test

instructions.
Bit 0 = C

Carry/borrow.

This bit is set and cleared b y hardware and soft­ware. It indicates an overflow or an underflow has
occurred during the last arithmetic operation.
0: No overflow or underflow has occurred.
1: An overflow or underflow has occurred.

This bit is driven by the SCF and RCF instructions
and tested by the JRC and JRNC instructions. It is
also affected by the “bit test and branch”, shift and
rotate instructions.

Interrupt Managem ent B i ts

Bit 5,3 = I1, I0

Interrupt

The combination of the I1 and I0 bits gives the cur­rent interrupt software priority.

Interrupt Software Priorit y I1 I0

Level 0 (main) 1 0
Level 1 0 1
Level 2 0 0
Level 3 (= interrupt disable) 1 1

These two bits are set/cleared b y hardware when
entering in interrupt. The loaded value is given by
the corresponding bits in the interrupt software pri­ority registers (IxSPR). They can be also set/
cleared by software with the RIM, SIM, IRET,
HALT, WFI and PUSH/POP instructions.

See the interrupt management chapter for more
details.

18/171

CENTRAL PROCESSING UNIT (Cont’d)

ST72260G, ST72262G, ST72264G

Stack Pointer (SP)

Read/Write
Reset Value: 01 7Fh

15 8

00000001

The least significant byte of the Stack Pointer
(called S) can be directly accessed by a LD in­struction.

Note: When the lower limit is exceeded, the Stack
Pointer wraps around to the stack upper limit, wi th­out indicating the s tack overflow. The previously
stored information is then o verwritten and there­fore lost. The stack also wraps in case of an under­flow.

70

SP7 SP6 SP5 SP4 SP3 SP2 SP1

SP0

The stack is used to save the retu rn address dur­ing a subroutine call and the CPU context during
an interrupt. The user may also directly manipulate
the stack by means of the PUSH and POP instruc-

The Stack Pointer is a 16-bit register which is al­ways pointing to the next free location in the stack.
It is then decremented after data has been pushed
onto the stack and incremented before data is
popped from the stack (see Figure 8).

Since the stack is 128 bytes deep, the 8 most sig­nificant bits are forced by hardw are. Following a n
MCU Reset, or after a Reset Stack Pointe r instruc­tion (RSP), the Stack Pointer contains its reset val­ue (the SP7 to SP0 bits are set) which is the stack

tions. In the case of an interrupt, the PCL is stored
at the first location point ed to by the SP. Then the
other registers are stored in the next locations as
shown in Figure 8

– When an interrupt is received, the SP is decre-

mented and the context is pushed on the stack.

– On return from interrupt, the SP is incremented

and the context is popped from the stack.

A subroutine call occupies two locations and an in­terrupt five locat ions i n the sta ck ar ea.

higher address.

Figure 8. Stack Manipulation Example

CALL

Subroutine

Interrupt

Event

PUSH Y POP Y IRET

RET

or RSP

@ 0100h

SP

@ 017Fh

SP

CC

A

X
PCH
PCL

PCH
PCL

Stack Higher Address = 017Fh
Stack Lower Address =

PCH

PCL

0100h

SP

Y

CC

A
X

PCH

PCL
PCH
PCL

SP

CC

A

X
PCH
PCL
PCH

PCL

SP

PCH
PCL

SP

19/171

ST72260G, ST72262G, ST72264G

6 SUPPLY, RESET AND CLOCK M ANAGEMENT

The device includes a range of utility features for
securing the application in critical situations (for
example in case of a power brown-out), and re­ducing the number of external components. An
overview is shown in Figure 10.

For more details, refer to dedicated parametric
section.

Main Features

■ Optional PLL for multiplying th e frequency by 2

(not to be used with internal RC oscillator)

■ Reset Sequence Manager (RSM)

■ Multi-Oscillator Clock Management (MO)

– 4 Crystal/ C e ra m ic res on ator oscilla t or s
– 1 Internal R C os c illa t or

■ System Integrity Management (SI)

– Main supply Low Voltage Detector (LVD)
– Auxiliary Voltage Detector (AVD) with inter-

rupt capability for monitori ng the main s upply

– Clock Security System (CSS) wi th Clo ck Filter

and Backup Safe Oscillator (enabled by op­tion byte)

Figure 10. Clock, Reset and Supply Block Diagram

SYSTEM INTEGRITYMANAGEMENT

6.1 PHASE LOCKED LOOP

If the clock frequency input to the PLL is in the 2 to
4 MHz range, the P LL can be used to mu ltiply the
frequency by two to obtain an f

of 4 to 8 MHz.

OSC2

The PLL is enable d by option byte. If the PLL is
disabled, then f

OSC2 = fOSC

/2.

Caution: T he PLL is not recom mended for appli­cations where timing accuracy is required. See
“PLL Characteristics” on page 134.

Figure 9. PLL Block Diagram

f

OSC

PLL x 2

/ 2

0

1

PLL OPTION BIT

f

OSC2

OSC2

OSC1

RESET

V

SS

V

DD

MULTI-

OSCILLATOR

(MO)

RESET SEQUENCE

MANAGER

(RSM)

f

OSC

PLL

(option)

f

OSC2

CLOCK SECURITYSYSTEM

CLOCK
FILTER

SICSR

AVD AVD

0

(CSS)

AVD Interrupt Requ est

LVD

F

RF

LOW VOLTAGE

DETECTOR

(LVD)

AUXILIARY VOLTAGE

DETECTOR

(AVD)

f

SAFE

OSC

CSS

0

IEIE

CSS Interrupt Request

OSC2

CSSDWDG

RF

MAIN CLOCK

CONTRO LLER

WITH REALTIME

CLOCK ( MCC/RTC)

WATCHDOG

TIMER (WDG )

f

CPU

20/171

6.2 MULTI-OSCILLATOR (MO)

ST72260G, ST72262G, ST72264G

The main clock of the ST7 can be generated by
four different source types coming from the multi­oscillator block:

■ an external source

■ 5 crystal or ceramic resonator oscillators

■ an internal high frequency RC oscillator

Each oscillator is optimized for a given frequenc y
range in terms of consumption and is selectable
through the option byte. The associated hardware
configurations are shown in Table 3. Refer to the
electrical characteristics section for more details.

Caution: The OS C1 and/or OSC2 pins must not
be left unconnected. For th e purposes of Failure
Mode and Effects Analysis, it should be noted that
if the OSC1 and/or OSC2 pin s are left unconnec t­ed, the ST7 main oscillat or may start and, in this
configuration, could generate an f

clock fre-

OSC

quency in excess of the allowed maximum
(>16MHz.), putting the ST7 in an unsafe/unde­fined state. The product behaviour must therefore
be considered undefined when the OSC pins are
left unconnected.

External Clock Source

In this external clock mode, a clock signal (square,
sinus or triangle) with ~50% duty cycle has to drive
the OSC1 pin while the OSC2 pin is tied to ground.

Crystal/Ceramic Oscillators

This family of oscillators has the advantage of pro­ducing a very accurate rate on the main clock of
the ST7. The select ion within a list of 5 oscillators
with different frequency ranges has to be done by
option byte in order to reduce c onsumption (refer
to Se ction 15.1 on page 157 for more details o n
the frequency ranges). In this mode of the m ulti­oscillator, the resonator and the load capacitors
have to be placed as close as possible to the oscil­lator pins in order to minimize output distortion and
start-up stabilization time. The loading capaci­tance values must be adjusted according to the
selected oscilla tor .

These oscillators are not stopped during the
RESET phase to avoid losing time in the oscillator
start-up phase.

Internal RC Oscillator

This oscillator allows a low cost solution for the
main clock of the ST7 using only an internal resis­tor and capacit or. Int er nal R C os cillator mode has
the drawback of a lower frequency accuracy and
should not be used in applications that require ac­curate timing .

In this mode, the two oscillator pins have to be tied
to ground.

Table 3. ST7 Clock Sources

Hardware Configur ation

ST7

OSC1 OSC2

External ClockCrystal/Cera mic ResonatorsInternal RC Oscillator

EXTERNAL

SOURCE

OSC1 O SC2

C

L1

CAPACITORS

OSC1 OSC2

ST7

LOAD

ST7

C

L2

21/171

ST72260G, ST72262G, ST72264G

6.3 RESET SEQUENCE MANAGER (RSM)

6.3.1 Introd uct i on

The reset sequence manager in cludes three RE­SET sources as shown in Figure 12:

■ External RESET source pulse

■ Internal LVD RESET (Low Voltage Detection)

■ Internal WATCHDOG RESET

These sources act on the RESET

pin and it is al-

ways kept low during the delay phase.
The RESET service routine vector is fixed at ad-

dresses FFFEh-FFFFh in the ST7 memory map.
The basic RESET s eque nc e cons i sts o f 3 p has es

as shown in F igure 11:

■ Active Phase depending on the RESET source

■ 4096 CPU clock cycle delay (selected by option

byte)

■ RESET vector fetch

The 4096 CPU clock cycle delay allows the oscil­lator to stabilise and ensures that recovery has
taken place from the Reset state. The shorter or
longer clock cycle delay should be selected by op­tion byte to correspond to the stabiliza tion time of
the external oscillator used in the appl icat ion.

Figure 12. Reset Block Diagram

The RESET vector fetch phase duration is 2 clock
cycles.

Figure 11. RESET Sequence Phases

RESET

Active Phase

INTERNAL RESET

4096 CLOCK CYCLES

6.3.2 Async hronous External R ESET

The RESET
output with integrated R

pin is both an input and an open-drain

weak pull-up resistor.

ON

FETCH

VECTOR

pin

This pull-up has no f ixed value but varies in ac­cordance with the input voltage. It

can be pulled
low by external circuitry to reset the device. See
Electrical Characteristic section for more details.

A RESET signal originating from an external
source must have a duration of at least t

h(RSTL)in

in
order to be recognized (see Figure 13). This de­tection is asynchronous and therefore the MCU
can enter reset state even in HALT mode.

RESET

V

DD

R

ON

Filter

PULSE

GENERATOR

INTERNAL
RESET

WATCHDOG RESE T
LVD RESET

22/171

RESET SEQUENCE MANAGER (Cont’d)
The RESET

pin is an asynchronous signal which
plays a major role in EMS performance. In a noisy
environment, it is recommended to follow the
guidelines mentioned in the electr ical characteris­tics section.

6.3.3 External Power-On RESET

If the LVD is disabled by option byte, to start up t he
microcontroller correctly, the user must ensure by
means of an external reset circuit that the reset
signal is held low until V
level specified for the selected f

A proper reset signal for a slow rising V

is over the m inimum

DD

frequency.

OSC

supply

DD

can generally be provide d by an ex ternal RC net­work connected to the RESET

pin.

Figure 13. RESET Sequences

V

DD

ST72260G, ST72262G, ST72264G

6.3.4 Internal Low Voltage Detector (LVD) RESET

Two differen t RESET sequences caused by the in­ternal LVD circuitry can be distinguished:

■ Power-On RESET

■ Voltage Drop RESET

The device RESET
pulled low when V
V

DD<VIT-

(falling edge) as shown in Figure 13.

The LVD filters spikes on V
avoid parasitic resets.

6.3.5 Internal Watchdog RESET

The RESET sequence generated by a internal
Watchdog counter overflow is shown in Figure 13.

Starting from the Watchdog counter underflow, the
device RESET
low during at least t

pin acts as an output that is

DD<VIT+

(rising edge) or

larger than t

DD

g(VDD)

pin acts as an output that is pulled

w(RSTL)out

.

to

V

IT+(LVD)

V

IT-(LVD)

EXTERNAL
RESET
SOURCE

RESET PIN

WATCHDOG
RESET

RUN

LVD

RESET

ACTIVE PHASE

RUN

t

h(RSTL)in

EXTERNAL

RESET

ACTIVE
PHASE

WATCHDOG UNDERFLOW

RUN RUN

INTERNAL RESET (4096 T
VECTOR FETCH

WATCHDO G

RESET

ACTIVE
PHASE

t

w(RSTL)out

CPU

)

23/171

ST72260G, ST72262G, ST72264G

6.4 SYSTEM INTEGRITY MANAGEMENT (SI)

The System Integrity Managem ent block contains
group the Low voltage Detector (LVD), Auxiliary
Voltage Detector (AVD) and Clock Security Sys­tem (CSS) functions. It is managed by the SICSR
register.

6.4.1 Low Voltage Detector (LVD)

The Low Voltage Detector funct ion (LVD) gener­ates a static reset when the V
below a V

reference value. This means that it

IT-

supply voltage is

DD

secures the power-up as well as the power-down
keeping the ST7 in reset.

The V
than the V

reference value for a voltage drop is lower

IT-

reference value for power-on in order

IT+

to avoid a parasitic reset when the MCU starts run­ning and sinks current on the supply (hysteresis).

The LVD Reset circuitry generates a reset when

is below:

V

DD

when VDD is rising

–V

IT+

–V

when VDD is falling

IT-

The LVD func t ion is illustrated in F igure 14.

Figure 14. Low Voltage Detector vs Reset

V

DD

The voltage threshold can be configured by option
byte to be low, medium or high.

Provided the minimum V
the oscillator frequency) is above V

value (guaranteed for

DD

, the MCU

IT-

can only be in two modes:

– under full software control
– in static safe reset

In these conditions, secure operation is always en­sured for the application without the need for ex­ternal reset hardware.

During a Low Voltage Detector Reset, the RESET
pin is held low, thus p ermitting the MCU to reset
other devices.

Notes:
The LVD allows the device to be used without any

external RESET circuitry.
The LVD is an optional function whi ch can be se-

lected by option byte.

V
V

RESET

IT+

IT-

V

hys

24/171

SYSTEM INTEGRITY MANAGEMENT (Cont’d)

6.4.2 Auxiliary Voltage Detector (AVD)

The Voltage Detector function (AVD) is based on
an analog comparison between a V
erence value and the V

main supply. The V

DD

and V

IT-

IT+

ref-

IT-

reference value for falling voltage is lower than the
V

reference value for rising voltage in order to

IT+

avoid parasitic detection (hysteresis).
The output of the AVD comparator is directly read-

able by the application software through a real
time status bit (VDF) in the SICSR register. This bit
is read only.

Caution: The AVD functions only if the LVD is en­abled through the option byte.

6.4.2.1 Monitoring the V

Main Su pply

DD

The AVD voltage threshold value is relative to the
selected LVD threshold configured by opt ion byte
(see Section 15.1 on page 157).

If the AVD interrupt is enabled, an interrupt is gen­erated when the voltage crosses the V
V

IT-(AVD)

threshold (AVDF bit toggles).

IT+(AVD)

or

ST72260G, ST72262G, ST72264G

In the case of a drop in voltage, the AVD i nterrupt
acts as an early warning, allowing software to shut
down safely before the LVD re sets the microcon­troller. See Figure 15 .

The interrupt on the rising edge is used to inform
the application that the V

If the voltage rise time t
CPU cycles (depending on the reset delay select­ed by option byte), no AVD interrupt will be gener­ated when V

is greater than 256 or 4096 cycles then:

If t

rv

IT+(AVD)

is reached.

– If the AVD interrupt is enabled before the

V

IT+(AVD)

threshold is reached, then 2 AVD inter­rupts will be received: the first when the AVDIE
bit is set, and the second when the threshold is
reached.

– If the AVD interrupt is enabled after the V

threshold is reached then only one AVD interrupt
will occur.

warning state is over.

DD

is less than 256 or 4096

rv

IT+(AVD)

Figure 15. Using the AVD to Monitor V

V

DD

DD

Early Warning Interrupt

(Power has dropped, MCU not
not yet in reset)

V

V

IT+(AVD)

V

IT-(AVD)

V

IT+(LVD)

V

IT-(LVD)

AVDF bit 0 0RESET VALUE

AVD INTERRUPT
REQUEST
IF AVDIE bit = 1

LVD RESET

1

hyst

INTERRUPT PROCESS

t

VOLTAGE RISE TIME

rv

1

INTERRUPT PROCESS

25/171

ST72260G, ST72262G, ST72264G

SYSTEM INTEGRITY MANAGEMENT (Cont’d)

6.4.3 Clock Security System (CSS)

The Clock Security System (CSS) protects the
ST7 against breakdowns, spikes and overfrequen­cies occurring on the main clock source (f
is based on a clock filter and a clock detection con­trol with an internal safe oscillator (f

SFOSC

6.4.3.1 Clock Filter Control

The PLL has an integrated glitch filtering capability
making it possible to protect the internal clock from
overfrequencies created by individual spikes. This
feature is available only when the P LL is enabled.
If glitches occur on f

(for example, due to loose

OSC

connection or noise), the CSS filters these auto­matically, so the internal CPU frequency (f
continues deliver a glitch-free signa l (see Figure

16).

6.4.3.2 Clock detection Control

If the clock signal disappears (due to a broken or
disconnected resona tor...), the safe osc illator de­livers a low frequency clock signal (f

SFOSC

allows the ST7 to perform some rescue opera­tions.

Automatically, the ST7 clock source switches back
from the safe o scillator (f
source (f

) recovers.

OSC

When the internal clock (f
oscillator (f

), the application software is noti-

SFOSC

) if the main clock

SFOSC

) is driven by the safe

CPU

fied by hardware setting the CSSD bit i n the SIC­SR register. An interrupt can be generated if the

OSC

).

CPU

) whi c h

). It

CSSIE bit has been previously set.
These two bits are described in the SICSR register
description.

6.4.4 Low Power Modes

Mode Description

WAIT

HALT

)

No effect on SI. CSS and AVD interrupts
cause the device to exit from Wait mode.

The SICSR register is frozen.
The CSS (including the safe oscillator) is
disabled until HALT mode is exited. The
previous CSS configuration resumes when
the MCU is woken up by an interrupt with
“exit from HALT mode” capability or from
the counter reset value when the MCU is
woken up by a RESET.

6.4.4.1 Interrupts

The CSS or AVD i nterrupt events generat e an in­terrupt if the corresponding Enable Control Bit
(CSSIE or AVDIE) is set and the interrupt mask in
the CC register is reset (RIM instruction).

Flag

Enable

Control

Bit

Interrupt Event

CSS event detection
(safe oscillator acti­vated as main clock)

AVD event AVDF AVDIE Yes No

Event

CSSD CSSIE Yes No

Exit
from
Wait

Exit

from

Halt

Figure 16. Clock Filter Function

Clock Filter Function

f

OSC2

PLL ON

f

CPU

Clock Detection Function

f

OSC2

f

SFOSC

f

CPU

26/171

ST72260G, ST72262G, ST72264G

SYSTEM INTEGRITY MANAGEMENT (Cont’d)

6.4.5 Register Description SYSTEM INTEGRITY (SI) CONTROL/ STATUS REGISTER (SICSR)

Read/Write
Reset Value: 000x 000x (00h)

70

AVDIEAVDFLVD

0

RF

CSSIECSSDWDG

0

RF

Bit 7 = Reserved, always read as 0.

Bit 6 = AVDIE

Voltage Detector interrupt enable

This bit is set and cleared by software. It enables
an interrupt to be generated when the AVDF flag
changes (toggles). The pending interrupt informa­tion is automatically cleared when software enters
the AVD interrupt routine.
0: AVD interrupt disabled
1: AVD interrupt enabled

Bit 5 = AVDF

Voltage Detector flag

This read-only bit is set and cleared by hardware.
If the AVDIE bit is set, an interrupt request is gen­erated when the AVDF bit changes value.

over V

0: V

DD

under V

1: V

DD

Bit 4 = LV DRF

IT+(AVD)

threshold

IT-(AVD)

threshold

LVD reset flag

This bit indicates that the last Reset was generat­ed by the LVD block. It is set by hardware (LVD re­set) and cleared by software (writing zero). See
WDGRF flag description for more details. When
the LVD is disabled by OPTION BYTE, the LVDRF
bit value is undefined.

Bit 3 = Reserved, must be kept cleared.

Bit 2 = CSSIE

Clock security syst. interrupt enable

This bit enables the interrupt when a disturbance
is detected by the Clock Security System (CSSD

bit set). It is set and cleared by software.
0: Clock security system interrupt disabled
1: Clock security system interrupt enabled
When the CSS is di sabled by O PTIO N B YTE, t he
CSSIE bit has no effect.

Bit 1 = CSSD

Clock security system detecti o n

This bit indicates that the safe oscillator of the
Clock Security System block has been selected by
hardware due to a dist urbance on the main clock
signal (f

). It is set by hardware and c lea red by

OSC

reading the SICSR register when the original oscil­lato r recove rs.
0: Safe oscillator is not active
1: Safe oscillator has been activated
When the CSS is di sabled by O PTIO N B YTE, t he
CSSD bit value is forced to 0.

Bit 0 = WDGRF

Watchdog reset flag

This bit indicates that the last Reset was generat­ed by the Watchdog p eripheral. It is set by hard­ware (watchdog reset) and cleared by software
(writing zero) or an LVD Reset (to ensure a stable
cleared state of the WDGRF flag when CPU
starts).
Combined with the LVDRF flag information, the
flag description is given by the following table.

RESET Sources LVDRF WDGRF

External RESET pin 0 0

Watchdog 0 1

LVD 1 X

Application Notes

The LVDRF flag is not cleared when another RE­SET type occurs (external or watchdog), the
LVDRF flag remains set to keep t race of the origi­nal failure. In this case, a watchdog reset can be
detected by software while an external reset can
not.

Address

(Hex.)

0025h

Register

Label

SICSR

Reset Value 0

76543210

AVDIE0AVDF0LVDRF

x0

CSSIE0CSSD0WDGRF

x

27/171

ST72260G, ST72262G, ST72264G

7 INTERRUPTS

7.1 INTRODUCTION

The ST7 enhanced interrupt management pro­vides the following features:

■ Hardware interrupts

■ Software interrupt (TRAP)

■ Nested or concurrent interrupt management

with flexible interrupt priority and level
management:

– Up to 4 software programmable nesting levels
– Up to 16 interrupt vectors fixed by hardware
– 2 non-maskable events: RESET and TRAP

This interrupt management is based on:
– Bit 5 and bit 3 of the CPU CC register (I1:0),
– Interrupt software priority registers (ISPRx),
– Fixed interrupt vector addresses located at the

high addresses of the memory map (FFE0h to
FFFFh) sorted by hardware priority order.

This enhanced interrupt controller guarantees full
upward compatibility with the standard (not nest­ed) ST7 interrupt controller.

7.2 MASKI NG AN D PROC ESSING FLOW

The interrupt masking is managed by the I1 and I0
bits of the CC register and the ISPRx registers
which give the interrupt software priority level of
each interrupt vector (see Table 4). The proc ess­ing flow is shown in Figure 17

When an interrupt request has to be serviced:
– Normal processing is suspended at the end of

the current instruction execution.

– The PC, X, A and CC registers are saved onto

the stack.

– I1 and I0 bits of CC register are set according to

the corresponding values in the ISPRx registers
of the serviced interrupt vector.

– The PC is then loaded with the interrupt vector of

the interrupt to service and the first instruction of
the interrupt service routine is fetched (refer to
“Interrupt Mapping” table for vector addresses).

The interrupt service routine should end with the
IRET instruction which causes the cont ents of the
saved registers to be recovered from the stack.

Note: As a consequence of the IRET instruction,
the I1 and I0 bits will be restored from the stack
and the program in the previous level will resume.

Table 4. Interrupt Software Priority Levels

Interrupt software priority Le vel I1 I0

Level 0 (main) Low
Level 1 0 1
Level 2 0 0
Level 3 (= interrupt disable) 1 1

High

10

Figure 17. Inte rru pt P rocessing Flowchart

RESET

RESTORE PC, X, A, CC

FROM STACK

28/171

PENDING

INTERRUPT

N

FETCH NEX T

INSTRUCTION

Y

“IRET”

N

EXECUTE

INSTRUCTION

Y

THE INTERRUPT
STAYS PENDING

Interrupt has the same or a

lower software priority

than current one

STACK PC, X, A, CC

LOA D I1:0 FROM IN TERR UPT SW REG .

LOAD PC FROM INTERRUPT VECTOR

I1:0

softwarepriorit y

than current one

Interrupt has a higher

INTERRUPTS (Cont’d)

ST72260G, ST72262G, ST72264G

Servicing Pe nding Interrup t s

As several interrupts can b e pending at the sam e
time, the interrupt to be taken into account is deter­mined by the following two-step process:

– the highest software priority interrupt is serviced,
– if several interrupts have the same software pri-

ority then the interrupt with the highest hardware
priority is serviced first.

Figure 18 describes this decision process.

Figure 18. Priority Decision Process

PENDING

INTERRUPTS

Same

HIGHEST HARDWARE

PRIORITY SERVICED

SOFTWARE

PRIORITY

HIGHEST SOFTWARE

PRIORITY SERVICED

Different

When an interrupt request is not serviced immedi­ately, it is latched and then processed when its
software priority combined with the hardware pri­ority becomes the highest one.

Note 1: The hardware priority is exclusive while
the software one is not. This allows the previ ous
process to succeed with only one interrupt.
Note 2: RESET and TRAP are non-maskable and
they can be considered as having the highest soft­ware priority in the decision process.

Different Interrupt Vector Sources

Two interrupt source types are managed by the
ST7 interrupt controller: the non-maskable type
(RESET and TRAP) and the maskable type (exter­nal or from internal peripherals).

Non-Maskable Sources

These sources are processed regardless of the
state of the I1 and I0 bits of the CC register (see

Figure 17). After stacking the PC, X, A and CC

registers (except for RESET), the corresponding
vector is loaded in the PC re gister and the I 1 and
I0 bits of the CC are set to disable interrupts (level

3). These sources allow the processor to exit
HALT mode.

■ TRAP (Non Maskable Software Interrupt)

This software interrupt is serviced when the TRAP
instruction is executed. It will be serviced accord­ing to the flowchart on Figure 17 as a TLI.

■ RESET

The RESET source has the highest priority in the
ST7. This means that the first current routine has
the highest software priority (level 3) and the high­est hardware priority.
See the RESET chapter for more details.

Maskable Sources

Maskable interrupt vect or sourc es can be serviced
if the corresponding interrupt is e nabled and if its
own interrupt software priority (in ISPRx registers)
is higher than the one currently being serviced (I1
and I0 in CC regist er). If any of these two condi­tions is false, the interrupt is la tched and thus re­mains pending.

■ External Interrupts

External interrupts allow the processor to exit from
HALT low power mode.
External interrupt sensitivity is software selectable
through the Miscellaneous registers (MISCRx).
External interrupt triggered on edge will be latched
and the interrupt request automatically cleared
upon entering the interrupt service routine.
If several input pins of a grou p connected to the
same interrupt vector request an interrupt simulta­neously, the interrupt vector w ill be se rv iced. Soft­ware can read the pin levels to identify which
pin(s) are the source of the interrupt.

If several input pins are selected simultaneously
as interrupt source, these are logically NANDed.
For this reason if o ne of the interrupt pins i s tied
low, it masks the other ones.

■ Peripheral Interrupts

Usually the peripheral interrupts cause the MCU to
exit from HALT mode except those mentioned in
the “Interrupt Mapping” table.
A peripheral interrupt occurs when a specific flag
is set in the peripheral status registers and if the
corresponding enable bit is set in the peripheral
control register.
The general sequence for clearing an interrupt is
based on an access to the status register followed
by a read or write to an associated register.
Note: The clearing sequence resets the internal
latch. A pending interrupt (i.e. waiting for being
serviced) will therefore be lost if the clear se­quence is executed.

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ST72260G, ST72262G, ST72264G

INTERRUPTS (Cont’d)

7.3 INTERRUPTS AND LOW POWER MODES

All interrupts allow the processor to exit the WAIT
low power mode. On the contrary, only external
and other specified interrupts allow the processor
to exit the HALT modes (see column “Exit from
HALT” in “Interrupt Mapping” table). When several
pending interrupts are present while exiting HALT
mode, the first one serviced can only be an inter­rupt with exit from HALT mode capability and it is
selected through the same decision process
shown in Figure 18.

Note: If an interrupt, that is not able to Exit from
HALT mode, is pending with the highest priority
when exiting HALT mode, this interrupt is serviced
after the first one serviced.

Figure 19. Concurren t Int errupt Management

IT1

TLI

IT3

IT0

TLI

IT1

RIM

IT2

IT1

IT4

IT2

HARDWARE PRIORITY

MAIN

11 / 10

7.4 CONCURRENT & NESTED MANAGEMENT

The following Figure 19 and Figure 20 show two
different interrupt management modes. The first is
called concurrent mode and does not allow an in­terrupt to be interrupted, unlike the nested mode in

Figure 20. The interrupt hardware priority is given

in this order from the l owest to the highest: MAIN,
IT4, IT3, IT2, IT1, IT0. The software priority is giv­en for each interrupt.

Warning: A stack overflow may occur without no­tifying the software of the failure.

Note: TLI (Top Level Interrupt) is not available in
thi s product.

SOFTWARE
PRIORITY
LEVEL

IT0

IT3

IT4

MAIN

3
3
3
3
3
3
3/0

I1

11
11
11
11
11
11

10

I0

USED STACK = 10 BYTES

Figure 20. Nested Interrupt Management

IT2

IT1

IT4

IT1

IT2

RIM

HARDWARE PRIORITY

MAIN

TLI

IT3

IT4 IT4

IT0

TLI

11 / 10

30/171

IT0

IT3

IT1

SOFTWARE
PRIORITY
LEVEL

IT2

10

MAIN

I1 I0

3
3
2
1
3
3
3/0

11
11
00
01
11
11

USED STACK = 20 BYTES