SGS Thomson Microelectronics ST62T30BM6, ST62T30BM3, ST62T30BB6, ST62T30BB3, ST62P30BM6 Datasheet

...
September 1998 1/86
Rev. 2.5
ST62T30B
ST62E30B
8-BIT OTP/EPROM MCUs WITH A/D CONVERTER,
16-BIT AUTO-RELOAD TIMER, EEPROM, SPI AND UART
3.0 to 6.0V Supply Operating Range
-40 to +125°C Operating Temperature Range
Run, Wait and Stop Modes
5 Interrupt Vectors
Look-up Table capability in Program Memory
Data Storage in Program Memory: User selectable size
Data RAM: 192 bytes
Data EEPROM: 128 bytes
User Programmable Options
20 I/O pins, fully programmable as:
– Input with pull-up resistor – Input without pull-up resistor – Input with interrupt generation – Open-drain or push-pull output – Analog Input
4 I/O lines can sinkup to 20mA to drive LEDs or
TRIACs directly
8-bit Timer/Counter with 7-bit programmable prescaler
16-bit Auto-reload Timer with 7-bit
programmable prescaler (AR Timer)
Digital Watchdog
8-bit A/D Converter with 16 analog inputs
8-bit Synchronous Peripheral Interface (SPI)
8-bit Asynchronous Peripheral Interface (UART)
On-chip Clock oscillator canbedriven by Quartz
Crystal or Ceramic resonator
Oscillator Safe Guard
One external Non-Maskable Interrupt
ST623x-EMU2 Emulation and Development
System (connects to an MS-DOS PC via a parallel port).
DEVICE SUMMARY
(See end of Datasheet for Ordering Information)
PDIP28
PS028
CDIP28W
DEVICE
OTP
(Bytes)
EPROM
(Bytes)
I/O Pins
ST62T30B 7948 - 20 ST62E30B 7948 20
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Table of Contents
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ST62T30B/ST62E30B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1 GENERAL DESCRIPTION . . . . . . . ...............................................5
1.1 INTRODUCTION .........................................................5
1.2 PIN DESCRIPTIONS . . .. . . . . . . ............................................7
1.3 MEMORYMAP ..........................................................8
1.3.1 Introduction . . . . . . . . ................................................8
1.3.2 Program Space . . . . . . . . . . . . . . . . . . . . . . . . . . . ..........................8
1.3.3 Data Space . . . . . . . . ...............................................10
1.3.4 Stack Space . . . . . . . . . . . . . . . . . ......................................10
1.3.5 Data Window Register (DWR) . . . . . . .. . .. . . . . . . . . . .....................11
1.3.6 Data RAM/EEPROM Bank Register (DRBR)..............................12
1.3.7 EEPROM Description ...............................................13
1.4 PROGRAMMING MODES .................................................15
1.4.1 Option Byte . . . . . . . . ...............................................15
1.4.2 Program Memory . . . . ...............................................15
1.4.3 EEPROM Data Memory . . .. . . . . . . . . ..................................15
1.4.4 EPROMErasing....................................................15
2 CENTRAL PROCESSING UNIT .................................................16
2.1 INTRODUCTION ........................................................16
2.2 CPU REGISTERS . . . . . . . . ...............................................16
3 CLOCKS, RESET, INTERRUPTS AND POWER SAVING MODES . . . . . . . ..............18
3.1 CLOCKSYSTEM........................................................18
3.1.1 Main Oscillator . . . . . . . . . . ...........................................18
3.1.2 Low Frequency Auxiliary Oscillator (LFAO). . . . . . . . . . . . . . . ................19
3.1.3 Oscillator Safe Guard. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . ................19
3.2 RESETS...............................................................22
3.2.1 RESET Input ......................................................22
3.2.2 Power-on Reset . . . . . . . . . . . . . . . .....................................22
3.2.3 Watchdog Reset . . . . ...............................................23
3.2.4 Application Notes . . . . ...............................................23
3.2.5 MCU Initialization Sequence ..........................................23
3.3 DIGITAL WATCHDOG . . . . . . . . . . . . . . . .....................................25
3.3.1 Digital Watchdog Register (DWDR). . . ..................................27
3.3.2 Application Notes . . . . ...............................................27
3.4 INTERRUPTS . . . . ......................................................29
3.4.1 Interrupt request . . . . . . . . . . . . . . . .....................................29
3.4.2 Interrupt Procedure . . . ..............................................30
3.4.3 Interrupt Option Register (IOR) . . . . ....................................31
3.4.4 Interrupt sources . . . . ...............................................31
3.5 POWER SAVING MODES .................................................34
3.5.1 WAIT Mode . . . . . . . . ...............................................34
3.5.2 STOPMode.......................................................34
3.5.3 Exit from WAIT and STOP Modes . . . ...................................35
4 ON-CHIP PERIPHERALS . . . ...................................................36
4.1 I/OPORTS.............................................................36
4.1.1 Operating Modes . . . . ...............................................37
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4.1.2 Safe I/O State Switching Sequence. . . ..................................38
4.1.3 ARTimer alternate functions ..........................................40
4.1.4 SPI alternate functions . . . ............................................40
4.1.5 UART alternate functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................40
4.1.6 I/O Port Option Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................42
4.1.7 I/O Port Data Direction Registers. . .....................................42
4.1.8 I/O Port Data Registers . . . . ..........................................42
4.2 TIMER ................................................................43
4.2.1 Timer Operating Modes . . .. . . . . . . . . ..................................44
4.2.2 Timer Interrupt . . . . . . . . . . ...........................................44
4.2.3 Application Notes . . . . ...............................................45
4.2.4 Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . .........................45
4.3 ARTIMER 16 . . . ........................................................46
4.3.1 CENTRAL COUNTER . . . ............................................47
4.3.2 SIGNAL GENERATION MODES . . .....................................48
4.3.3 TIMINGS MEASUREMENT MODES. . ..................................50
4.3.4 INTERRUPT CAPABILITIES ..........................................52
4.3.5 CONTROL REGISTERS . . . ..........................................53
4.3.6 16-BIT REGISTERS . . . . . . . . ........................................55
4.4 A/D CONVERTER (ADC) . . . ..............................................57
4.4.1 Application Notes . . . . ...............................................57
4.5 U. A. R. T. (UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER). ..........59
4.5.1 PORTS INTERFACING . . . . . . . . . . . . ..................................59
4.5.2 CLOCK GENERATION . . . . ..........................................60
4.5.3 DATA TRANSMISSION . . .. . . . . . . . . ..................................60
4.5.4 DATA RECEPTION .................................................61
4.5.5 INTERRUPT CAPABILITIES ..........................................61
4.5.6 REGISTERS ......................................................61
4.6 SERIAL PERIPHERAL INTERFACE (SPI) . . . . . . . . . . . . ........................63
5SOFTWARE ................................................................65
5.1 ST6 ARCHITECTURE . . . . . . . . . . . . . . . .....................................65
5.2 ADDRESSING MODES . . . . ...............................................65
5.3 INSTRUCTION SET . . . ...................................................66
6 ELECTRICAL CHARACTERISTICS. . . . . . . . . . . . ..................................71
6.1 ABSOLUTE MAXIMUM RATINGS. ..........................................71
6.2 RECOMMENDED OPERATING CONDITIONS. . . ..............................72
6.3 DC ELECTRICAL CHARACTERISTICS ......................................73
6.4 AC ELECTRICAL CHARACTERISTICS ......................................74
6.5 A/D CONVERTER CHARACTERISTICS. . . ...................................74
6.6 TIMER CHARACTERISTICS . . . ............................................75
6.7 .SPI CHARACTERISTICS .................................................75
6.8 ARTIMER16 ELECTRICAL CHARACTERISTICS. . . . . . . . . . . . . . . ................75
7 GENERAL INFORMATION . . .. . . . . . . ...........................................76
7.1 PACKAGE MECHANICAL DATA. . . . ........................................76
7.2 .ORDERING INFORMATION. . . ............................................77
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ST62P30B . ........................................79
1 GENERAL DESCRIPTION . . . . . . . ..............................................80
1.1 INTRODUCTION ........................................................80
1.2 ORDERING INFORMATION ...............................................80
1.2.1 Transfer of Customer Code . ..........................................80
1.2.2 Listing Generation and Verification . . . . . . . . . . ...........................80
ST6230B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
1 GENERAL DESCRIPTION . . . . . . . ..............................................84
1.1 INTRODUCTION ........................................................84
1.2 ROM READOUT PROTECTION . . . . . . . . . . . . . . . . . . . . ........................84
1.3 ORDERING INFORMATION ...............................................86
1.3.1 Transfer of Customer Code . ..........................................86
1.3.2 Listing Generation and Verification . . . . . . . . . . ...........................86
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ST62T30B ST62E30B
1 GENERAL DESCRIPTION
1.1 INTRODUCTION
The ST62T30B and ST62E30B devices are low cost members of the ST62xx 8-bit HCMOS family of microcontrollers, which is targeted at low to me­dium complexity applications. All ST62xx devices are based on a building block approach: a com-
mon core is surrounded by a number of on-chip peripherals.
The ST62E30B is the erasable EPROM version of the ST62T30B device, which may be used to em­ulate the ST62T30B device, as well as the respec­tive ST6230B ROM devices.
Figure 1. Block Diagram
TEST
NMI INTERRUPT
PROGRAM
PC
STACK LEVEL 1 STACK LEVEL 2 STACK LEVEL 3 STACK LEVEL 4 STACK LEVEL 5 STACK LEVEL 6
POWER SUPPLY
OSCILLATOR
RESET
DATA ROM
USER
SELECTABLE
DATA RAM
PORT A
PORT B
TIMER
DIGITAL
8 BIT CORE
TEST/V
PP
8-BIT
A/D CONVERTER
PA0..PA1 / 20 mA Sink
V
DDVSS
OSCin OSCout RESET
WATCHDOG
Memory
PORT C
SPI (SERIAL
PERIPHERAL
INTERFACE)
AUTORELOAD
TIMER
192 Bytes
7948
bytes
DATA EEPROM
128 Bytes
PA2/OVF/ 20mA Sink PA3/PWM/20 mA Sink
PA4/Ain/CP1
PA5/Ain/CP2
PB4..PB6/Ain
PC4..PC7/Ain
PORT D
PD6,PD7/Ain
PD1/Ain/Scl PD2/Ain/Sin PD3/Ain/Sout PD4/Ain/RXD1 PD5/Ain/TXD1
(V
PP
on EPROM/OTP versions only)
TIMER
VR01823F
UART
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ST62T30B ST62E30B
INTRODUCTION (Cont’d)
OTP and EPROM devices are functionally identi­cal. TheROM based versions offer the same func­tionality selecting as ROM options the options de­fined in the programmable option byte of the OTP/EPROM versions.OTP devices offer all the advantages of user programmability at low cost, which make them the ideal choice in a wide range of applications where frequent code changes, mul­tiple code versions or last minute programmability are required.
Figure 2. ST62T30B/E30B Pin Configuration
These compact low-cost devices feature a Timer comprising an 8-bit counter and a 7-bit program­mable prescaler, an 16-bit Auto-Reload Timer, with 2 input capture channels, EEPROM data ca­pability, a serial synchronous port communication interface (SPI), a serial asynchronous port inter­face (UART), an 8-bit A/D Converter with 16 ana­log inputs and a Digital Watchdog timer, making them well suited for a wide range of automotive, appliance and industrial applications.
1 2 3 4 5 6 7 8 9 10 11 12 13
14
15
16
17
18
19
20
V
DD
TIMER
OSCin
OSCout
NMI
TEST/V
PP
(1)
RESET
Ain/PC7 Ain/PC6 Ain/PC5
V
SS
PA0 PA1 PA2/OVF PA3/PWM
PD3/Ain/Sout PD4/Ain/RXD1 PD5/Ain/TXD1 PD6/Ain
PD7/Ain
28 27 26 25 24 23 22 21
Ain/PC4
Ain/PB6 Ain/PB5
Ain/PB4
PA4/Ain/CP1 PA5/Ain/CP2 PD1/Ain/Scl PD2/Ain/Sin
(1)
V
PP
on EPROM/OTP only
VR01804B
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ST62T30B ST62E30B
1.2 PIN DESCRIPTIONS VDDand V
SS
. Power is supplied to the MCU via these two pins. VDDis the power connection and VSSis the ground connection.
OSCin and OSCout. These pins are internally connected to the on-chip oscillator circuit. A quartz crystal, a ceramic resonator or an external clock signal can be connected between these two pins. The OSCin pin is the input pin, the OSCout pin is the output pin.
RESET
. The active-low RESET pin is used to re-
start the microcontroller. TEST/VPP. The TEST must be held at VSSfor nor-
mal operation. If TEST pin is connected to a +12.5V level during the reset phase, the EPROM/OTP programming Mode is entered.
NMI.
The NMI pin provides the capability for asyn­chronous interruption, by applying an external non maskable interrupt to the MCU.The NMI input is falling edge sensitive with Schmitt trigger charac­teristics. The user can select as option the availa­bility of an on-chip pull-up at this pin.
PA0-PA5. These 6 lines are organised as one I/O port (A). Each line may be configured under soft­ware control as inputs with or without internal pull­up resistors, interrupt generating inputs with pull­up resistors, open-drain or push-pull outputs. PA2/OVF, PA3/PWM, PA4/CP1 and PA5/CP2 can be used respectively as overflow outputpin, output compare pin, and astwo input capture pins for the embedded 16-bit Auto-Reload Timer.
In addition, PA4-PA5 can also be used as analog inputs for the A/D converter while PA0-PA3 can sink 20mA for direct LED or TRIAC drive.
PB4-PB6.
These 3 lines are organised as one I/O port (B). Each line may be configured under soft­ware control as inputs with or without internal pull­up resistors, interrupt generating inputs with pull­up resistors, open-drain or push-pull outputs, an­alog inputs for the A/D converter.
PC4-PC7
. These 4 lines are organised as one I/O port (C). Each line may be configured under soft­ware control as input with or without internal pull­up resistor, interrupt generating input with pull-up resistor, analog input for the A/D converter, open­drain or push-pull output.
PD1-PD7. These 7 lines are organised as one I/O port (portD). Each line may be configured under software control as input with or without internal pull-up resistor, interrupt generating input with pull-up resistor, analog input open-drain or push­pull output. In addition, the pins PD5/TXD1 and PD4/RXD1 can be used as UART output (PD5/TXD1) or UARTinput (PD4/RXD1). The pins PD3/Sout, PD2/Sin and PD1/SCL can also be used respectively as data out, data in and Clock pins for the on-chip SPI.
TIMER. This isthe TIMER 1I/O pin. Ininput mode, it is connected to the prescaler and acts as ex­ternal timer clock or as control gate for the internal timer clock. In output mode, theTIMER pinoutputs the data bit when a time-out occurs.The user can select as option the availability of an on-chip pull­up at this pin.
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ST62T30B ST62E30B
1.3 MEMORY MAP
1.3.1 Introduction
The MCU operates in three separate memory spaces: Program space, Data space, and Stack space. Operation in these three memory spaces is described in the following paragraphs.
Briefly, Program space contains user program code in Program memory and user vectors; Data space contains user data in RAM and in Program memory, and Stack space accommodates six lev­els of stack for subroutine and interrupt service routine nesting.
1.3.2 Program Space
Program Space comprises the instructions to be executed, the data required for immediate ad­dressing mode instructions, the reserved factory test area and the user vectors. Program Space is addressed via the 12-bit Program Counter register (PC register).
Program Space is organised in four 2K pages. Three of them are addressed in the 000h-7FFh lo­cations of the Program Space by the Program Counter and by writing the appropriate code in the Program ROM Page Register (PRPR register). A
common (STATIC) 2K page is available all the time for interrupt vectors and common subrou­tines, independently of the PRPR register content. This “STATIC” page is directly addressed in the 0800h-0FFFh by the MSB of the Program Counter register PC 11. Note this page can also be ad­dressed in the 000-7FFh range. It is two different ways of addressing the same physical memory.
Jump from a dynamic page to another dynamic page is achieved by jumping back to the static page, changing contents of PRPR and then jump­ing to the new dynamic page.
Figure 3. 8Kbytes Program Space Addressing
Figure 4. Memory Addressing Diagram
PC SPACE
000h
7FFh 800h
FFFh
0000h
1FFFh
Page 0
Page 1
Static Page
Page 2 Page 3
Page 1
Static Page
ROM SPACE
PROGRAM SPACE
PROGRAM
INTERRUPT &
RESET VECTORS
ACCUMULATOR
DATA RAM
BANK SELECT
WINDOW SELECT
RAM
X REGISTER Y REGISTER V REGISTER
W REGISTER
DATA READ-ONLY
WINDOW
RAM / EEPROM BANKING AREA
000h
03Fh 040h
07Fh 080h 081h 082h 083h 084h
0C0h
0FFh
0-63
DATA SPACE
0000h
0FF0h
0FFFh
MEMORY
MEMORY
DATA READ-ONLY
MEMORY
VR01568
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ST62T30B ST62E30B
MEMORY MAP (Cont’d) Table 1. ST62E30B/T30B Program Memory Map
Note: OTP/EPROM devices can be programmed
withthe development toolsavailablefrom STMicro­electronics (ST62E3X-EPB or ST623X-KIT).
1.3.2.1 Program ROM Page Register (PRPR)
The PRPR register can be addressed like a RAM location in the Data Space at the address CAh; nevertheless it is a write only register that cannot be accessed with single-bit operations. This regis­ter is used to select the 2-Kbyte ROM bank of the Program Space that will be addressed. The number of the page has to be loaded in the PRPR register. Refer to the Program Space description for additional information concerning the use of this register. The PRPR register is not modified when an interrupt or a subroutine occurs.
Care is required when handling the PRPR register as it is write only. For this reason, it is not allowed to change the PRPR contents while executing in­terrupt service routine, as the service routine cannot save and then restore its previous content. This operation may be necessary if common rou­tines and interrupt service routines take more than 2K bytes; in this case it could be necessary to di­vide the interrupt service routine into a (minor) part in the static page (start and end) and to a second (major) part in one of the dynamic pages. If it is im­possible to avoid thewriting of this register in inter­rupt service routines, an image of this register must be saved in a RAM location, and each time the program writes to the PRPR it must write also to the image register. The image register must be written before PRPR, so if an interrupt occurs be­tween the two instructions the PRPR is not af­fected.
Program ROM Page Register (PRPR)
Address: CAh Write Only
Bits 2-7= Not used. Bit 5-0 = PRPR1-PRPR0:
Program ROM Select.
These two bits select the corresponding page to be addressed in the lower part of the 4K program address space as specified inTable 2.
This register is undefined on Reset. Neither read nor single bit instructions may be used to address this register.
Table 2.8Kbytes Program ROM Page Register
Coding
1.3.2.2 Program Memory Protection
The Program Memory in OTP or EPROM devices can be protected against external readout of mem­ory by selecting the READOUT PROTECTION op­tion in the option byte.
In the EPROM parts, READOUT PROTECTION option can be disactivated only by U.V. erasure that also results into the whole EPROM context erasure.
Note: Once the Readout Protection is activated, it is no longer possible, even for STMicroelectronics, to gain access to the Program memory contents. Returned parts with a protection set can therefore not be accepted.
ROM Page Device Address Description
Page 0
0000h-007Fh 0080h-07FFh
Reserved
User ROM
Page 1 “STATIC”
0800h-0F9Fh 0FA0h-0FEFh 0FF0h-0FF7h 0FF8h-0FFBh
0FFCh-0FFDh
0FFEh-0FFFh
User ROM
Reserved
Interrupt Vectors
Reserved
NMI Vector
Reset Vector
Page 2
0000h-000Fh
0010h-07FFh
Reserved
User ROM
Page 3
0000h-000Fh
0010h-07FFh
Reserved
User ROM
70
- - - - - - PRPR0 PRPR1
PRPR1 PRPR0 PC bit 11 Memory Page
X X 1 Static Page (Page 1) 0 0 0 Page 0 0 1 0 Page 1 (Static Page 1 0 0 Page 2 1 1 0 Page 3
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ST62T30B ST62E30B
MEMORY MAP (Cont’d)
1.3.3 Data Space
Data Space accommodates all the data necessary for processing the user program. This space com­prises the RAM resource, the processor core and peripheral registers, as well as read-only data such as constants and look-up tables in Program memory.
1.3.3.1 Data ROM
All read-only data is physically stored in program memory, which also accommodates the Program Space. The program memory consequently con­tains the program code to be executed, as well as the constants and look-up tables required by the application.
The Data Space locations in which the different constants and look-up tables are addressed by the processor core may be thought of as a 64-byte window through which it is possible to access the read-only data stored in Program memory.
1.3.3.2 Data RAM/EEPROM
In ST6230B and ST62E30B devices, the data space includes 60 bytes of RAM, the accumulator (A), the indirect registers (X), (Y), the short direct registers (V), (W), the I/O port registers, the pe­ripheral data and control registers, the interrupt option register and the Data ROM Window register (DRW register).
Additional RAM and EEPROM pages can also be addressed using banks of 64 bytes located be­tween addresses 00h and 3Fh.
1.3.4 Stack Space
Stack space consists of six 12-bit registers which are used to stack subroutine and interrupt return addresses, as well as the current program counter contents.
Table 3. Additional RAM/EEPROM Banks.
Table 4. ST62T30B/E30B Data Memory Space
Device RAM EEPROM
ST62T30B/E30B 2 x 64 bytes 2 x 64 bytes
DATAand EEPROM
000h 03Fh
DATA ROM WINDOW AREA
040h
07Fh X REGISTER 080h Y REGISTER 081h V REGISTER 082h
W REGISTER 083h
DATARAM
084h
0BFh PORT A DATA REGISTER 0C0h PORT B DATA REGISTER 0C1h PORT C DATA REGISTER 0C2h PORT D DATA REGISTER 0C3h
PORT A DIRECTION REGISTER 0C4h PORT B DIRECTION REGISTER 0C5h PORT C DIRECTION REGISTER 0C6h PORT D DIRECTION REGISTER 0C7h
INTERRUPT OPTION REGISTER 0C8h*
DATA ROM WINDOWREGISTER 0C9h*
ROM BANK SELECT REGISTER 0CAh*
RAM/EEPROMBANK SELECTREGISTER 0CBh*
PORT A OPTION REGISTER 0CCh
PORT B OPTION REGISTER 0CDh PORT C OPTION REGISTER 0CEh PORT D OPTION REGISTER 0CFh
A/D DATA REGISTER 0D0h
A/D CONTROL REGISTER 0D1h
TIMER 1 PRESCALER REGISTER 0D2h
TIMER 1 COUNTER REGISTER 0D3h
TIMER 1 STATUS/CONTROLREGISTER 0D4h
RESERVED 0D5h
UART DATASHIFT REGISTER 0D6h
UARTSTATUS CONTROL REGISTER 0D7h
WATCHDOG REGISTER 0D8h
RESERVED 0D9h
I/O INTERRUPT POLARITY REGISTER 0DAh
OSCILLATOR CONTROL REGISTER 0DBh
SPI INTERRUPT DISABLEREGISTER 0DCh*
SPI DATA REGISTER 0DDh
RESERVED 0DEh
EEPROM CONTROL REGISTER 0DFh ARTIM16 COMPAREMASK REG. LOW BYTE MASK 0E0h ARTIM16 2ND STATUSCONTROL REGISTERSCR2 0E1h ARTIM16 3RD STATUSCONTROL REGISTERSCR3 0E2h ARTIM16 4TH STATUSCONTROL REGISTER SCR4 0E3h ARTIM16 1ST STATUSCONTROL REGISTER SCR1 0E8h
ARTIM16 RELOAD CAPTURE REG. HIGH BYTE RLCP 0E9h
ARTIM16 RELOAD CAPTURE REG. LOW BYTE RLCP 0EAh
ARTIM16 CAPTURE REGISTER HIGH BYTECP 0EBh
ARTIM16 CAPTURE REGISTER LOW BYTE CP 0ECh ARTIM16COMPAREVALUE REGISTERHIGHBYTECMP 0EDh ARTIM16COMPAREVALUEREGISTERLOWBYTECMP 0EEh
ARTIM 16 COMPARE MASK REG. HIGH BYTE MASK 0EFh
RESERVED
0F0h
0FBh
RESERVED
OFCh
0FDh 0FEh
ACCUMULATOR OFFh
* WRITE ONLY REGISTER
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ST62T30B ST62E30B
MEMORY MAP (Cont’d)
1.3.5 Data Window Register (DWR)
The Dataread-only memory window is locatedfrom address 0040h to address 007Fh in Data space. It allows direct reading of 64 consecutive bytes locat­ed anywhere in program memory, between ad­dress 0000h and 1FFFh (top memory address de­pends on the specific device). All the program memory can therefore be used to store either in­structions or read-only data. Indeed, the window can be moved in steps of 64 bytes along the pro­grammemory by writingtheappropriate codeinthe Data Window Register (DWR).
The DWRcan be addressed like any RAM location in the Data Space, it is however a write-only regis­ter and therefore cannot be accessed using single­bit operations. This register is used to position the 64-byte read-only data window (from address 40h to address 7Fh of the Data space) in program memory in 64-byte steps. The effective address of the byte to be read as data in program memory is obtained by concatenating the 6 least significant bits of the register address given in the instruction (as least significant bits) and the content of the DWR register (as most significantbits), as illustrat­ed inFigure 5below. For instance, when address­ing location 0040h of the Data Space, with 0 load­ed in the DWR register, the physical location ad­dressed in program memory is 00h. The DWR reg­ister is not cleared on reset, therefore it must be written to prior tothe first access to the Data read­only memory window area.
Data Window Register (DWR)
Address: 0C9h Write Only
Bits 7 = Not used. Bit 6-0 =
DWR5-DWR0:
Data read-only memory
Window Register Bits.
These are the Data read­only memory Window bits that correspond to the upper bits of the data read-only memory space.
Caution:
This register is undefined on reset. Nei­ther read nor single bit instructions may beused to address this register.
Note:
Care is required when handling the DWR register as it is write only. For this reason, the DWR contents should not be changed while exe­cuting an interrupt service routine, as the service routine cannot save and then restore the register’s previous contents. If it is impossible to avoid writ­ing to theDWR during the interrupt service routine, an image of the register must be saved in a RAM location, and each time the program writes to the DWR, it must also write to the image register. The image register must be written first so that, if an in­terrupt occurs between the two instructions, the DWR is not affected.
Figure 5. Data read-only memory Window Memory Addressing
70
- DWR6 DWR5 DWR4 DWR3 DWR2 DWR1 DWR0
DATA ROM
WINDOW REGISTER
CONTENTS
DATA SPACE ADDRESS
40h-7Fh
IN INSTRUCTION
PROGRAM SPACE ADDRESS
765432 0
543210
543210
READ
1
67891011
0
1
VR0A1573
12
1
0
DATA SPACE ADDRESS
59h
0000
0
1
00
1
11
Example:
(DWR)
DWR=28h
11000000001
ROM
ADDRESS:A19h
11
13
01
27
12/86
ST62T30B ST62E30B
MEMORY MAP (Cont’d)
1.3.6 Data RAM/EEPROM Bank Register (DRBR)
Address: CBh Write only
Bit 7-5 = These bits are not used Bit 4 - DRBR4. This bit, when set, selects RAM
Page 2. Bit 3 - DRBR3. This bit, when set, selects RAM
Page 1. Bit2. This bit is not used. Bit 1 - DRBR1. This bit, when set, selects
EEPROM Page 1. Bit 0 - DRBR0. This bit, when set, selects
EEPROM Page 0. The selection of the bank ismade byprogramming
the Data RAM Bank Switch register (DRBR regis­ter) located at address CBh of the Data Space ac­cording to Table 1. No more than one bank should be set at a time.
The DRBR register can be addressed like a RAM Data Space at the address CBh; nevertheless it is a write only register that cannot be accessed with single-bit operations. This register is used to select the desired 64-byte RAM/EEPROM bank of the Data Space. The number of banks has to be load­ed in the DRBR register and the instruction has to point to the selected location as if it was in bank 0 (from 00h address to 3Fh address).
This register is not cleared during the MCU initiali­zation, therefore it must be written before the first access to the Data Space bank region. Refer to the Data Space description for additional informa­tion. The DRBR register is not modified when an interrupt or a subroutine occurs.
Notes: Care isrequired when handling the DRBR register
as it is write only. For this reason, it is not allowed to change the DRBR contents while executing in­terrupt service routine, as the service routine can­not save and then restore its previous content. If it is impossible to avoid the writing of this register in interrupt service routine, an image of this register must be saved in a RAM location, and each time the program writes to DRBR it must write also to the image register. The image register must be written first, so if an interrupt occurs between the two instructions the DRBR is not affected.
In DRBR Register, only 1 bit must be set. Other­wise two or more pages are enabled in parallel, producing errors.
Table 5. Data RAM Bank Register Set-up
70
- - - DRBR4 DRBR3 - DRBR1 DRBR0
DRBR ST62T30B/E30B
00 None 01 EEPROM Page 0 02 EEPROM Page 1 08 RAM Page 1
10h RAM Page2
other Reserved
28
13/86
ST62T30B ST62E30B
MEMORY MAP (Cont’d)
1.3.7 EEPROM Description
EEPROM memory is located in 64-byte pages in data space. This memory may be used by the user program for non-volatile data storage.
Data space from 00h to 3Fh is paged as described in Table 6. EEPROM locations are accessed di­rectly by addressing these paged sections of data space.
The EEPROM does not require dedicated instruc­tions for read orwriteaccess.Once selected via the Data RAM Bank Register, the active EEPROM page is controlled bythe EEPROM Control Regis­ter (EECTL), which is described below.
BitE20FF oftheEECTLregister mustbereset prior to any write or read access to the EEPROM. If no bank hasbeenselected, orifE2OFF is set,any ac­cess is meaningless.
Programming must be enabled by setting the E2ENA bit of the EECTL register.
The E2BUSYbit of the EECTL register is setwhen the EEPROM is performing a programming cycle. Any access to the EEPROM when E2BUSY is set is meaningless.
Provided E2OFF and E2BUSY are reset, an EEP­ROM location is read just like any other data loca­tion, also in terms of access time.
Writing to the EEPROM may be carried out in two modes: Byte Mode (BMODE) and Parallel Mode
(PMODE). In BMODE, one byte is accessed at a time, while in PMODE up to 8 bytes in the same row are programmed simultaneously (with conse­quent speed and power consumption advantages, the latter being particularly important in battery powered circuits).
General Notes: Data should be written directly to the intended ad-
dress in EEPROM space. There is no buffer mem­ory between data RAM and the EEPROM space.
When the EEPROM is busy (E2BUSY = “1”) EECTL cannot be accessed in write mode, it is only possible to read the status of E2BUSY. This implies that as long as the EEPROM is busy, it is not possible to change the status of the EEPROM Control Register. EECTL bits 4 and 5 are reserved and must never be set.
Care is requiredwhen dealing with the EECTL reg­ister, as some bits are write only. For this reason, the EECTL contents must not be altered while ex­ecuting an interrupt service routine.
If it is impossible to avoid writing to this register within an interrupt service routine, an image of the register must be saved in a RAM location, and each time the program writes to EECTL it must also writeto the image register. The image register must be written to first so that, if an interrupt oc­curs between the two instructions, the EECTL will not be affected.
Table 6. Row Arrangement for Parallel Writing of EEPROM Locations
Dataspace addresses. Banks 0 and 1.
Byte 01234567 ROW7 38h-3Fh ROW6 30h-37h ROW5 28h-2Fh ROW4 20h-27h ROW3 18h-1Fh ROW2 10h-17h ROW1 08h-0Fh ROW0 00h-07h
Up to 8 bytes in each row may be programmed simultaneously in Parallel Write mode.
The number of available 64-byte banks (1 or 2) is device dependent.
29
14/86
ST62T30B ST62E30B
MEMORY MAP (Cont’d) Additional Notes on Parallel Mode:
If the user wishes to perform parallel program­ming, the first step should be to set the E2PAR2 bit. From this time on, the EEPROM will be ad­dressed in write mode, the ROW address will be latched and it will be possible to change it only at the end of the programming cycle, or by resetting E2PAR2 without programming the EEPROM. Af­ter the ROW address is latched, the MCU can only “see” the selected EEPROM row and any attempt to write or read other rows will produce errors.
The EEPROM should not be read while E2PAR2 is set.
As soon as the E2PAR2 bit is set, the 8 volatile ROW latches are cleared. From this moment on, the user can load data in all or in part of the ROW. Setting E2PAR1 will modify the EEPROM regis­ters corresponding to the ROW latches accessed after E2PAR2. For example, if the software sets E2PAR2 and accesses the EEPROM by writing to addresses 18h, 1Ah and 1Bh, and then sets E2PAR1, these three registers will be modified si­multaneously; the remaining bytes in the row will be unaffected.
Note that E2PAR2 is internally reset at the end of the programming cycle. This implies that the user must set the E2PAR2 bit between two parallel pro­gramming cycles. Note that if the user tries to set E2PAR1 while E2PAR2 is not set, there will be no programming cycle and theE2PAR1 bit will be un­affected. Consequently, the E2PAR1 bit cannot be set if E2ENA is low. The E2PAR1 bit can be set by the user, only if the E2ENA and E2PAR2 bits are also set.
EEPROM Control Register (EECTL)
Address: DFh — Read/Write Reset status: 00h
Bit 7 =D7:
Unused.
Bit6=E2OFF:
Stand-by Enable Bit.
WRITE ONLY. Ifthisbitis settheEEPROMisdisabled(any access willbemeaningless) andthepowerconsumption of the EEPROM is reduced to its lowest value.
Bit 5-4 =D5-D4:
Reserved.
MUST be kept reset.
Bit 3 =
E2PAR1
:
Parallel Start Bit.
WRITE ONLY. OnceinParallelMode,assoonastheusersoftware sets the E2PAR1 bit, parallel writing of the 8 adja­cent registers will start. This bitisinternally reset at the end of the programming procedure. Note that less than 8 bytes can bewritten ifrequired, the un­defined bytes being unaffected by the parallel pro­gramming cycle; this is explained in greater detail in the Additional Notes on Parallel Mode overleaf.
Bit 2 = E2PAR2:
Parallel Mode En. Bit.
WRITE ONLY. This bit must be setby the user program in order to perform parallel programming. If E2PAR2 is set and the parallel start bit (E2PAR1) is reset, up to 8 adjacent bytes can be written simultane­ously. These 8 adjacent bytes are considered as a row, whose address lines A7, A6, A5, A4, A3 are fixed while A2, A1andA0 arethe changing bits, as illustrated in Table 6. E2PAR2 is automatically re­set at the end of any parallel programming proce­dure. It can be reset by the user software before starting the programming procedure, thus leaving the EEPROM registers unchanged.
Bit 1 = E2BUSY:
EEPROM Busy Bit.
READ ON­LY. This bit is automatically set by the EEPROM control logic when the EEPROM is in program­ming mode. The user program should test it before any EEPROM read or write operation; any attempt to access the EEPROM while the busy bit is set will be aborted and the writing procedure in progress will be completed.
Bit 0 = E2ENA:
EEPROM Enable Bit.
WRITE ON­LY. This bit enables programming of the EEPROM cells. It must be set before any write to the EEP­ROM register. Any attempt to write to the EEP­ROM when E2ENA is low is meaningless and will not trigger a write cycle.
70
D7 E2OFF D5 D4 E2PAR1 E2PAR2 E2BUSY E2ENA
30
15/86
ST62T30B ST62E30B
1.4 PROGRAMMING MODES
1.4.1 Option Byte
The Option Byte allows configuration capability to the MCUs. Option byte’s content is automatically read, and the selected options enabled, when the chip reset is activated.
It can only be accessed during the programming mode. This access is made either automatically (copy from a master device) or by selecting the OPTION BYTE PROGRAMMING mode ofthe pro­grammer.
The option byte is located in a non-user map. No address has to be specified.
EPROM Code Option Byte
Bit 7. Reserved. Bit 6 =
PORT PULL
. This bit must be set high to have pull-up input state at reset on the I/O port. When this bit is low, I/O ports are in input without pull-up (high impedance) state at reset
Bit 5 =
EXTCNTL
. This bit selects the External STOP Mode capability. When EXTCNTL is high, pin NMI controls if the STOP mode can be ac­cessed when the watchdog is active. When EXTC­NTL is low, the STOP instruction is processed as a WAIT as soon as the watchdog is active.
Bit 4 = PROTECT. This bit allows the protection of the software contents against piracy. When the bit PROTECT is set high, readout of the OTP con­tents is prevented by hardware. No programming equipment is able to gain access to the user pro­gram. When this bit is low, the user program can be read.
Bit 3 =TIM PULL.This bit must be set high tocon­figure the TIMER pin with a pull up resistor. When it is low, no pull up is provided.
Bit 2 =NMI PULL. This bit mustbe set high tocon­figure the NMI pin with a pull up resistor when it is low, no pull up is provided.
Bit 1 = WDACT. This bit controls the watchdog ac­tivation. When it is high, hardware activation is se­lected. The software activation is selected when WDACT is low.
Bit 0 =OSGEN.This bit must be set high to enable the oscillator Safe Guard. When this bit is low, the OSG is disabled.
The Option byte is written during programming ei­ther by using the PC menu (PC driven Mode) or automatically (stand-alone mode)
1.4.2 Program Memory
EPROM/OTP programming mode is set by a +12.5V voltage applied to the TEST/VPPpin. The programming flow of the ST62T30B/E30B is de­scribed in the User Manual of the EPROM Pro­gramming Board.
The MCUs can be programmed with the ST62E3xB EPROM programming tools available from STMicroelectronics.
1.4.3 EEPROM Data Memory
EEPROM data pages are supplied in the virgin state FFh. Partial or total programming of EEP­ROM data memory can be performed either through the application software, or through an ex­ternal programmer. Any STMicroelectronics tool used for the program memory (OTP/EPROM) can also be used to program the EEPROM data mem­ory.
1.4.4 EPROM Erasing
The EPROM of the windowed package of the MCUs may be erased by exposure to Ultra Violet light. The erasure characteristic of the MCUs is such that erasure begins when the memory is ex­posed to light with a wave lengths shorter than ap­proximately 4000Å. It should be noted that sun­lights and some types of fluorescent lamps have wavelengths in the range 3000-4000Å.
It is thus recommended that the window of the MCUs packages becovered by an opaque label to prevent unintentional erasure problems when test­ing the application in such an environment.
The recommended erasure procedure of the MCUs EPROM is the exposure to short wave ul­traviolet light which have a wave-length 2537A. The integrated dose (i.e. U.V. intensity x exposure time) for erasure should be a minimum of 15W­sec/cm2. The erasure time with this dosage is ap­proximately 15 to 20 minutes using an ultraviolet lamp with 12000µW/cm2power rating. The ST62E30B should be placed within 2.5cm (1Inch) of the lamp tubes during erasure.
70
-
PORT
PULL
EXTCNTLPROTECT
TIM
PULL
NMI
PULL
WDACT OSGEN
31
16/86
ST62T30B ST62E30B
2 CENTRAL PROCESSING UNIT
2.1 INTRODUCTION
The CPUCoreofST6devicesisindependent ofthe I/O or Memory configuration. As such, it may be thought of as an independent central processor communicating with on-chip I/O, Memory and Pe­ripherals via internal address, data, and control buses. In-core communication is arranged as shown in Figure 6; the controller being externally linked to both the Reset and Oscillator circuits, while the core islinked to the dedicated on-chip pe­ripherals via the serial data bus and indirectly, for interrupt purposes, through the control registers.
2.2 CPU REGISTERS
TheST6FamilyCPUcorefeaturessixregistersand three pairs of flags available to the programmer. These are described in the following paragraphs.
Accumulator (A). The accumulator is an 8-bit general purpose register used in all arithmetic cal­culations, logical operations, and data manipula­tions. The accumulator can be addressed in Data space asa RAM location ataddress FFh. Thus the ST6 can manipulate the accumulator just like any other register in Data space.
Indirect Registers (X, Y).These two indirect reg­isters are used as pointers to memory locations in Data space. They are used in the register-indirect addressing mode. These registers can be ad­dressed in the data space as RAM locations at ad­dresses 80h (X) and 81h (Y). They can also be ac­cessed with the direct, shortdirect, or bit direct ad­dressing modes. Accordingly, the ST6 instruction set can use the indirect registers as any other reg­ister of the data space.
Short Direct Registers (V, W).These two regis­ters are used to save a byte in short direct ad­dressing mode. They can be addressed in Data space as RAM locations at addresses 82h (V) and 83h (W). They can also be accessed using the di­rect and bit direct addressing modes. Thus, the ST6 instruction set can use the short direct regis­ters as any other register of the data space.
Program Counter (PC). The program counter is a 12-bit register which contains the address of the next ROM location to be processed by the core. This ROM location may be an opcode, an oper­and, or the address of an operand. The 12-bit length allows the direct addressing of 4096 bytes in Program space.
Figure 6. ST6 Core Block Diagram
PROGRAM
RESET
OPCODE
FLAG
VALUES
2
CONTROLLER
FLAGS
ALU
A-DATA
B-DATA
ADDRESS/READ LINE
DATA SPACE
INTERRUPTS
DATA
RAM/EEPROM
DATA
ROM/EPROM
RESULTS TO DATA SPACE (WRITE LINE)
ROM/EPROM
DEDICATIONS
ACCUMULATOR
CONTROL
SIGNALS
OSCin
OSCout
ADDRESS
DECODER
256
12
Program Counter
and
6 LAYER STACK
0,01 TO 8MHz
VR01811
32
17/86
ST62T30B ST62E30B
CPU REGISTERS (Cont’d)
However, ifthe program space contains more than 4096 bytes, the additional memory in program space can be addressed by using the Program Bank Switch register.
The PC value is incremented after reading the ad­dress of the current instruction. To execute relative jumps, the PC and the offset are shifted through the ALU, where they are added; the result is then shifted back into the PC. The program counter can be changed in the following ways:
- JP (Jump) instructionPC=Jump address
- CALL instructionPC= Call address
- Relative Branch Instruction.PC= PC +/- offset
- Interrupt PC=Interrupt vector
- Reset PC= Reset vector
- RET & RETI instructionsPC= Pop (stack)
- Normal instructionPC= PC + 1
Flags (C, Z). The ST6 CPU includes three pairs of flags (Carry and Zero), each pairbeing associated with one of the three normal modes of operation: Normal mode, Interrupt mode and Non Maskable Interrupt mode. Each pair consists of a CARRY flag and a ZERO flag. One pair (CN, ZN) is used during Normal operation, another pair is used dur­ing Interrupt mode (CI, ZI), and a third pair is used in the Non Maskable Interrupt mode (CNMI, ZN­MI).
The ST6 CPU uses the pair of flags associated with the current mode: as soon as an interrupt (or a Non Maskable Interrupt) is generated, the ST6 CPU uses the Interrupt flags (resp. the NMI flags) instead of the Normal flags. When the RETI in­struction is executed, the previously used set of flags is restored. It should be noted that each flag set can only be addressed in its own context (Non Maskable Interrupt, Normal Interrupt or Main rou­tine). The flags are not cleared during context switching and thus retain their status.
The Carry flag is set when a carry or a borrow oc­curs during arithmetic operations; otherwise it is cleared. The Carry flag is also set to the value of the bit tested in a bit test instruction; it also partici­pates in the rotate left instruction.
The Zero flag is set if the result of the last arithme­tic or logical operation was equal to zero; other­wise it is cleared.
Switching between the three sets of flags is per­formed automatically when an NMI, an interrupt or a RETI instructions occurs. As the NMI mode is
automatically selected after the reset of the MCU, the ST6 core uses at first the NMI flags.
Stack. The ST6 CPU includes a true LIFO hard­ware stack which eliminates the need for a stack pointer. The stack consists of six separate 12-bit RAM locations that do not belong to the data space RAM area. When a subroutine call (or inter­rupt request) occurs, the contents of each level are shifted into the next higher level, while the content of the PC is shifted into the first level (the original contents of the sixth stack level are lost). When a subroutine or interrupt return occurs (RETor RETI instructions), the first level register is shifted back into the PC and the value of each level is popped back into the previous level. Since the accumula­tor, in common with all other data space registers, is not stored in this stack, management of these registers should be performed within the subrou­tine. The stack will remain in its “deepest” position if more than 6 nested calls or interrupts are execut­ed, and consequently the last return address will be lost. It will also remain in its highest position if the stack is empty and a RET or RETI is executed. In this case the next instruction will be executed.
Figure 7. ST6 CPU Programming Mode
l
SHORT
DIRECT
ADDRESSING
MODE
V REGISTER
WREGISTER
PROGRAM COUNTER
SIX LEVELS
STACK REGISTER
CZNORMAL FLAGS
INTERRUPT FLAGS
NMI FLAGS
INDEX
REGISTER
VA000423
b7
b7
b7
b7
b7
b0
b0
b0
b0
b0
b0b11
ACCUMULATOR
YREG.POINTER
XREG.POINTER
CZ
CZ
33
18/86
ST62T30B ST62E30B
3 CLOCKS, RESET, INTERRUPTS AND POWER SAVING MODES
3.1 CLOCK SYSTEM
The MCU features a Main Oscillator which can be driven by an external clock, or used in conjunction with an AT-cut parallel resonant crystal or a suita­ble ceramic resonator. In addition, a Low Frequen­cy Auxiliary Oscillator (LFAO) can be switched in for security reasons, to reduce power consump­tion, or to offer the benefits of a back-up clock sys­tem.
The Oscillator Safeguard (OSG) option filters spikes from the oscillator lines, provides access to the LFAO to provide a backup oscillator in the event of main oscillator failure and also automati­cally limits the internal clock frequency (f
INT
)asa function ofVDD, in order to guarantee correct oper­ation. These functions are illustrated inFigure 9, Figure 10, Figure 11 and Figure 12.
Figure 8 illustrates various possible oscillator con­figurations using anexternal crystalorceramic res­onator, anexternal clockinputorthelowestcostso­lution using onlytheLFAO.CL1an CL2should have acapacitance intherange12to22pFforanoscillator frequency in the 4-8 MHz range.
The internal MCU clock frequency (f
INT
) is divided by 12 to drive the Timer and the Watchdog timer, and by 13 to drive the CPU core, while the A/D converter is driven by f
INT
divided either by 6 or by
12 as may be seen inFigure 11. With an 8MHz oscillator frequency, thefastest ma-
chine cycle is therefore 1.625µs. A machine cycleis the smallest unit oftime needed
toexecute any operation (for instance, to increment the Program Counter). An instruction may require two, four, or five machine cycles for execution.
3.1.1 Main Oscillator
The main oscillator can be turned off (when the OSG ENABLED option is selected) by setting the OSCOFF bit of the OSCR Control Register. The Low Frequency Auxiliary Oscillator is automatical­ly started.
Figure 8. Oscillator Configurations
INTEGRATEDCLOCK
OSG ENABLED option
OSC
in
OSC
out
C
L1n
C
L2
ST6xxx
CRYSTAL/RESONATOR CLOCK
OSC
in
OSC
out
ST6xxx
EXTERNAL CLOCK
NC
OSC
in
OSC
out
ST6xxx
NC
VA0016
VA0015A
34
19/86
ST62T30B ST62E30B
CLOCK SYSTEM (Cont’d)
Turning on the main oscillator is achieved by re­setting the OSCOFF bit of the OSCR Register or by resetting the MCU. Restarting the main oscilla­tor implies a delay comprising the oscillator start up delay period plus the duration of the software instruction at f
LFAO
clock frequency.
3.1.2 Low Frequency Auxiliary Oscillator
(LFAO)
The Low Frequency Auxiliary Oscillator has three main purposes. Firstly, it can be used to reduce power consumption in non timing critical routines. Secondly, it offers a fully integrated system clock, without any external components. Lastly, it acts as a safety oscillator in case of main oscillator failure.
This oscillator is available when the OSG ENA­BLED option is selected. In this case, it automati­cally starts one of its periods after the first missing edge from the main oscillator, whatever the reason (main oscillator defective, no clock circuitry provid­ed, main oscillator switched off...).
User code, normal interrupts, WAIT and STOP in­structions, are processed as normal, at the re­duced f
LFAO
frequency. The A/D converter accura­cy is decreased, since theinternal frequency isbe­low 1MHz.
At power on, the Low Frequency Auxiliary Oscilla­tor starts faster than the Main Oscillator. It there­fore feeds the on-chip counter generating thePOR delay until the Main Oscillator runs.
The Low Frequency Auxiliary Oscillator is auto­matically switched off as soon as the main oscilla­tor starts.
OSCR
Address: 0DBh Read/Write
Bit 7-1= These bits are not used and must be kept cleared after reset.
Bit 0 =
OSCOFF
.
Main oscillator turn-off.
When low, this bit enables main oscillator to run. The main oscillator is switched off when OSCOFF is high.
3.1.3 Oscillator Safe Guard
The Oscillator Safe Guard (OSG) affords drastical­ly increased operational integrity in ST62xx devic­es. The OSG circuit provides three basic func­tions: it filters spikes from the oscillator lines which would result in over frequency to the ST62 CPU; it gives access to the Low Frequency Auxiliary Os­cillator (LFAO), used to ensure minimum process­ing in case of main oscillator failure, to offer re­duced power consumption or to provide a fixed fre­quency low cost oscillator; finally, it automatically limits the internal clock frequency as a function of supply voltage, in order to ensure correct opera­tion even if the power supply should drop.
The OSG is enabled or disabled by choosing the relevant OSG option. It may be viewed as a filter whose cross-over frequency is device dependent.
Spikes on the oscillator linesresult in aneffectively increased internal clock frequency. In the absence of an OSG circuit, this may lead to an over fre­quency for a given power supply voltage. The OSG filters out such spikes (asillustrated inFigure
9). In all cases, when the OSG is active, the maxi­mum internal clock frequency, f
INT
, is limited to
f
OSG
, which is supply voltage dependent. This re-
lationship is illustrated inFigure 12. When the OSG is enabled, the Low Frequency
Auxiliary Oscillator may be accessed. This oscilla­tor starts operating after the first missing edge of the main oscillator (seeFigure 10).
Over-frequency, at a given power supply level, is seen by the OSG as spikes; it therefore filters out some cycles in order that the internal clock fre­quency of the device is kept within the range the particular device can stand (depending on VDD), and below f
OSG
: the maximum authorised frequen-
cy with OSG enabled. Note. The OSGshould beused whereverpossible
as it provides maximum safety. Care must be tak­en, however, as it can increase power consump­tion and reduce the maximum operating frequency to f
OSG
.
70
-------
OSC OFF
35
20/86
ST62T30B ST62E30B
CLOCK SYSTEM (Cont’d) Figure 9. OSG Filtering Principle
Figure 10. OSG Emergency Oscillator Principle
(1)
VR001932
(3)
(2)
(4)
(1) (2)
(3) (4)
Maximum Frequency for the device to work correctly Actual Quartz Crystal Frequency at OSCin pin
Noise from OSCin Resulting Internal Frequency
Main
VR001933
Internal
Emergency
Oscillator
Frequency
Oscillator
36
21/86
ST62T30B ST62E30B
CLOCK SYSTEM (Cont’d) Figure 11. Clock Circuit Block Diagram
Figure 12. Maximum Operating Frequency (f
MAX
) versus Supply Voltage (VDD)
Notes
:
1. In this area, operation is guaranteed at the quartz crystal frequency.
2. Whenthe OSG isdisabled, operation in this area is guaranteed atthe crystalfrequency. When the OSG is enabled, operation in this area is guaranteed at a frequency of at least f
OSG Min.
3. When the OSG is disabled, operation in this area is guaranteed at the quartz crystal frequency. When the OSG is enabled, access to this area is prevented. The internal frequency is kept a f
OSG.
4. When the OSG is disabled, operation in this area is not guaranteed When the OSG is enabled, access to this area is prevented. The internal frequency is kept at f
OSG.
MAIN
OSCILLATOR
OSG
LFAO
M U
X
Core
:13
:12
:1
TIMER 1
Watchdog
POR
f
INT
Main Oscillator off
ADC
ARTIMER 16
:6
M U
X
1
2.5
3.5 4 4.5 5 5.5 6
8
7
6
5
4
3
2
Maximum FREQUENCY (MHz)
SUPPLY VOLTAGE (V
DD
)
FUNCTIONALITY IS NOT
3
4
3
2
1
f
OSG
f
OSG
Min
GUARANTEED
IN THIS AREA
VR01807
37
22/86
ST62T30B ST62E30B
3.2 RESETS
The MCU can be reset in three ways: – by the external Reset input being pulled low; – by Power-on Reset; – by the digital Watchdog peripheral timing out.
3.2.1 RESET Input
The RESET pin may be connected to a device of the application board in order to reset the MCU if required. The RESET pin may be pulled low in RUN, WAIT or STOP mode. This input can be used to reset the MCU internal state and ensure a correct start-up procedure. The pin is active low and features a Schmitt trigger input. The internal Reset signal is generated by adding a delay to the external signal. Therefore even short pulses on the RESET pin are acceptable, provided VDDhas completed its rising phase and that the oscillator is running correctly (normal RUN or WAIT modes). The MCU is kept in the Reset state as long as the RESET pin is held low.
If RESET activation occurs in the RUN or WAIT modes, processing of the user program is stopped (RUN mode only), the Inputs and Outputs are con­figured as inputs with pull-up resistors and the main Oscillator is restarted. When the level on the RESET pin then goes high, the initialization se­quence is executed following expiry of the internal delay period.
If RESET pin activation occurs in the STOP mode, the oscillator starts up and all Inputs and Outputs are configured as inputs with pull-up resistors. When the level of theRESET pin then goes high, the initialization sequence is executed following expiry of the internal delay period.
3.2.2 Power-on Reset
The function of the POR circuit consists in waking up the MCU at an appropriate stage during the power-on sequence. At the beginning of this se­quence, the MCU is configured in the Reset state: all I/O ports are configured as inputs with pull-up resistors and no instruction is executed. When the power supply voltage rises toa sufficient level, the oscillator starts to operate, whereupon an internal delay is initiated, in order to allow the oscillator to fully stabilize before executing the first instruction. The initialization sequence isexecuted immediate­ly following the internal delay.
The internal delay isgenerated byanon-chip coun­ter.The internal reset lineis released 2048 internal clock cycles after release of the external reset.
Notes:
To ensure correct start-up, the user should take care that the reset signal is notreleased before the VDDlevel is sufficient to allow MCU operation at the chosen frequency (see Recommended Oper­ating Conditions).
A proper reset signal for a slow rising VDDsupply can generally be provided by an external RC net­work connected to theRESET pin.
Figure 13.Reset and Interrupt Processing
INT LATCHCLEARED
NMI MASK SET
RESET
( IFPRESENT )
SELECT
NMI MODE FLAGS
IS RESET STILL
PRESENT?
YES
PUT FFEH
ON ADDRESSBUS
FROM RESET LOCATIONS
FFE/FFF
NO
FETCH INSTRUCTION
LOAD PC
VA000427
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RESETS (Cont’d)
3.2.3 Watchdog Reset
The MCU provides a Watchdog timer function in order to ensure graceful recovery from software upsets. If the Watchdog register is not refreshed before an end-of-count condition is reached, the internal reset will be activated. This, amongst oth­er things, resets the watchdog counter.
The MCU restarts just as though the Reset had been generated by the RESET pin, including the built-in stabilisation delay period.
3.2.4 Application Notes
No external resistor is required between VDDand the Reset pin, thanks to the built-in pull-up device.
The POR circuit operates dynamically, in that it triggers MCU initialization on detecting the rising edge of VDD. The typical threshold is in the region of 2 volts, but the actual value of the detected threshold depends on the way in which VDDrises.
The POR circuit is
NOT
designed to supervise
static, or slowly rising or falling VDD.
3.2.5 MCU Initialization Sequence
When a reset occurs the stack is reset, the PC is loaded with the address of the Reset Vector (locat­ed in program ROM starting at address 0FFEh). A jump to the beginning of the user program must be coded at this address. Following a Reset, the In­terrupt flag is automatically set, so that the CPU is in Non Maskable Interrupt mode; this prevents the
initialisation routine from being interrupted. The in­itialisation routine should therefore be terminated by a RETI instruction, in order to revert to normal mode and enable interrupts. If no pending interrupt is present at the endofthe initialisation routine, the MCU will continue by processing the instruction immediately following the RETIinstruction. If, how­ever, a pending interrupt is present, it will be serv­iced.
Figure 14.Reset and Interrupt Processing
Figure 15. Reset Block Diagram
RESET
RESET
VECTOR
JP
JP:2 BYTES/4 CYCLES
RETI
RETI: 1 BYTE/2CYCLES
INITIALIZATION
ROUTINE
VA00181
V
DD
RESET
300k
2.8k
POWER
WATCHDOG RESET
CK
COUNTER
RESET
ST6 INTERNAL RESET
f
OSC
RESET
ON RESET
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RESETS (Cont’d) Table 7. Register Reset Status
Register Address(es) Status Comment
Oscillator Control Register EEPROM Control Register Port Data Registers Port Direction Register Port Option Register Interrupt Option Register TIMER Status/Control
AR TIMER Status/Control 1 Register AR TIMER Status/Control 2 Register AR TIMER Status/Control 3 Register AR TIMER Status/Control 4 Register
SPI Registers
0DBh 0DFh 0C0h to0C2h 0C4h to0C6h 0CCh to0CEh 0C8h 0D4h
0E8h 0E1h 0E2h OE3h
0DCh to0DDh
00h
Main oscillator on EEPROM enabled
I/O are Input with or without pull-up depending on PORTPULL option
Interrupt disabled TIMER disabled
AR TIMER stopped
SPI disabled
X, Y, V,W, Register Accumulator Data RAM Data RAM Page REgister Data ROM Window Register EEPROM A/D Result Register AR TIMER Capture Register AR TIMER Reload/Capture Register ARTIMER Mask Registers ARTIMER Compare Registers
080H TO083H 0FFh 084h to0BFh 0CBh 0C9h 00h to03Fh 0D0h 0DBh 0D9h OE0h-OEFh OEDh-OEEh
Undefined As written if programmed
TIMER Counter Register TIMER Prescaler Register Watchdog Counter Register A/D Control Register
0D3h 0D2h 0D8h 0D1h
FFh 7Fh
FEh
40h
Max count loaded
A/D in Stand-by
UART Control UART Data Register
OD7h OD6h
UART disabled
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3.3 DIGITAL WATCHDOG
The digital Watchdog consists of a reloadable downcounter timer which can be used to provide controlled recovery from software upsets.
The Watchdog circuit generates a Reset when the downcounter reaches zero. User software can prevent this reset by reloading the counter, and should therefore be written so that the counter is regularly reloaded while the user program runs correctly. In the event of a software mishap (usual­ly caused by externally generated interference), the user program will no longer behave in its usual fashion and the timer register will thus not be re­loaded periodically. Consequently the timer will decrement down to 00h and reset the MCU. In or­der to maximise the effectiveness of theWatchdog function, user software must be written with this concept in mind.
Watchdog behaviour is governed by two options, known as “WATCHDOG ACTIVATION” (i.e. HARDWARE or SOFTWARE) and “EXTERNAL STOP MODE CONTROL” (seeTable 8).
In the SOFTWARE option, the Watchdog is disa­bled until bit C of the DWDR register has been set.
When the Watchdog is disabled, low power Stop mode is available. Once activated, the Watchdog cannot be disabled, except by resetting the MCU.
In the HARDWARE option, the Watchdog is per­manently enabled. Since the oscillatorwill run con­tinuously, low power mode is not available. The STOP instruction is interpreted as a WAIT instruc­tion, and the Watchdog continues to countdown.
However, when the EXTERNAL STOP MODE CONTROL option has been selected low power consumption may be achieved in Stop Mode.
Execution of the STOP instruction is then gov­erned by a secondary function associated with the NMI pin. If a STOP instruction is encountered when the NMI pin is low, it isinterpreted as WAIT, as described above. If, however, the STOP in­struction is encountered when the NMI pin is high, the Watchdog counter is frozen and the CPU en­ters STOP mode.
When theMCU exits STOP mode (i.e. when an in­terrupt is generated), the Watchdog resumes its activity.
Table 8. Recommended Option Choices
Functions Required Recommended Options
Stop Mode& Watchdog “EXTERNAL STOP MODE” & “HARDWARE WATCHDOG”
Stop Mode “SOFTWARE WATCHDOG”
Watchdog “HARDWARE WATCHDOG”
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DIGITAL WATCHDOG(Cont’d)
The Watchdog is associated with a Data space register (Digital WatchDog Register, DWDR, loca­tion 0D8h) which is described in greater detail in Section 3.3.1 Digital Watchdog Register (DWDR). This register is set to 0FEh on Reset: bit C is cleared to “0”, which disables the Watchdog; the timer downcounter bits, T0 to T5, and the SR bit are allset to “1”, thus selecting the longest Watch­dog timer period. This time period can beset to the user’s requirements by setting the appropriate val­ue for bits T0 to T5 in the DWDR register. The SR bit must be set to “1”, since it is this bit which gen­erates the Reset signal when it changes to “0”; clearing this bit would generate an immediate Re­set.
It should be noted that the order of the bits in the DWDR register is inverted with respect to the as­sociated bits in the down counter: bit 7 of the DWDR register corresponds, in fact, to T0 and bit 2 to T5. The user should bear in mind the fact that these bits are inverted and shifted with respect to the physical counter bits when writing to this regis­ter. The relationship between the DWDR register bits and the physical implementation of the Watch­dog timer downcounter is illustrated inFigure 16.
Only the 6 most significant bits may be used to de­fine the time period, since it is bit 6 which triggers the Reset when it changes to “0”. This offers the user a choice of 64 timed periods ranging from 3,072 to 196,608 clock cycles (with an oscillator frequency of 8MHz, this isequivalent to timer peri­ods ranging from 384µs to 24.576ms).
Figure 16.Watchdog Counter Control
WATCHDOG CONTROL REGISTER
D0
D1
D3
D4
D5
D6
D7
WATCHDOG COUNTER
C
SR
T5
T4
T3
T2
T1
D2
T0
OSC÷12
RESET
VR02068A
÷
2
8
42
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