SGS Thomson Microelectronics ST62T62CM6, ST62T62CM3, ST62T62CB6, ST62T62CB3, ST62T52CM6 Datasheet

...
November 1999 1/78
Rev. 2.7
ST62T52C
ST62T62C/E62C
8-BIT OTP/EPROM MCUs WITH A/D CONVERTER,
SAFE RESET, AUTO-RELOAD TIMER AND EEPROM
3.0 to 6.0V Supply Operating Range
-40 to+125°C Operating TemperatureRange
Run, Wait and Stop Modes
5 InterruptVectors
Look-up Table capability in Program Memory
Data Storage in Program Memory:
User selectable size
Data RAM: 128 bytes
DataEEPROM: 64 bytes(noneonST62T52C)
User Programmable Options
9 I/Opins, 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
5 I/Olines can sinkupto30mA todriveLEDs or
TRIACs directly
8-bit Timer/Counter with 7-bit programmable
prescaler
8-bit Auto-reload Timerwith 7-bit programmable
prescaler (AR Timer)
Digital Watchdog
Oscillator SafeGuard
Low Voltage Detector for Safe Reset
8-bit A/D Converter with 4 analog inputs
On-chip Clockoscillator canbe drivenbyQuartz
Crystal Ceramic resonator or RCnetwork
User configurable Power-on Reset
One external Non-Maskable Interrupt
ST626x-EMU2 Emulation and Development
System (connects to an MS-DOS PC via a parallel port)
DEVICE SUMMARY
DEVICE
EPROM
(Bytes)
OTP
(Bytes)
EEPROM
ST62T52C 1836 ­ST62T62C 1836 64 ST62E62C 1836 64
(See end of Datasheet for Ordering Information)
PDIP16
PSO16
CDIP16W
SSOP16
1
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Table of Contents
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Document
Page
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ST62T52C/ST62T62C/E62C ............................1
1 GENERAL DESCRIPTION . .. . . . ................................................ 5
1.1 INTRODUCTION . . . . . .. . . . . . . ............................................ 5
1.2 PIN DESCRIPTIONS . . . . . . ................................................6
1.3 MEMORY MAP . . . . . . . . . . ................................................7
1.3.1 Introduction . . . ..................................................... 7
1.3.2 Program Space . . . . . . . . . . . . . . . . . . . .................................. 8
1.3.3 Data Space . . . . . . . . . . . . . . . . . . . . . . . . ................................ 9
1.3.4 Stack Space . . . . . . . . . . . . ............................................9
1.3.5 Data Window Register (DWR) . ........................................10
1.3.6 Data RAM/EEPROM Bank Register (DRBR) . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3.7 EEPROM Description . . . . . . . . . . . . . . .. . . . . ........................... 12
1.4 PROGRAMMING MODES . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.4.1 Option Bytes . . . . . . . . . . . . . . .. . . . . . . . . .............................. 14
1.4.2 Program Memory . . . ................................................ 14
1.4.3 . EEPROM Data Memory . . . . ......................................... 15
2 CENTRAL PROCESSING UNIT . . ............................................... 16
2.1 INTRODUCTION . . . . . .. . . . . . . ........................................... 16
2.2 CPU REGISTERS . . . .................................................... 16
3 CLOCKS, RESET, INTERRUPTS AND POWERSAVING MODES . . ...................18
3.1 CLOCK SYSTEM . . . . . . . . . . . . . ........................................... 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 LVD Reset . . . . .. . . . ............................................... 23
3.2.5 Application Notes . . . ................................................23
3.2.6 MCU Initialization Sequence . . . . . . . . ..................................24
3.3 DIGITAL WATCHDOG . . . . . . . . . . .. . . . . . . .................................. 26
3.3.1 Digital Watchdog Register (DWDR) . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3.2 Application Notes . . . ................................................28
3.4 INTERRUPTS . . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . .. . . . . . . .. .. . . . . 30
3.4.1 Interrupt request . ...................................................30
3.4.2 Interrupt Procedure . . . . . . . . . . . . . . .. ................................. 31
3.4.3 Interrupt Option Register(IOR) . . . . . . . . . . . . . . . . . . . .. . . . . ............... 32
3.4.4 Interrupt Sources . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . 32
3.5 POWER SAVING MODES . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ 34
3.5.1 WAIT Mode ....................................................... 34
3.5.2 STOP Mode . .. . . . . . ...............................................34
3.5.3 Exit from WAIT and STOP Modes . . . . ..................................35
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4 ON-CHIP PERIPHERALS . . . .. . . . . . . ...........................................36
4.1 I/O PORTS . . . . . . .. . . . . . . . . . ............................................ 36
4.1.1 Operating Modes . . . . . . .. . . . .. . . . .. . . . . . . ........................... 37
4.1.2 Safe I/O State Switching Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . 38
4.1.3 ARTimer alternate functions . . . . .. . . . . . . . . . ........................... 40
4.2 TIMER . . . . . . . . . . . . .. . . . . . . .. .. . . . . . . . ................................. 41
4.2.1 Timer Operation . . . . . . . .. . . . . . . . . . . . . . .............................. 42
4.2.2 Timer Interrupt . . . . . . . . . . . . . . . . . . . . . ................................ 42
4.2.3 Application Notes . . . ................................................42
4.2.4 Timer Registers . . . . . ...............................................43
4.3 AUTO-RELOAD TIMER . . . . . . . . . . . . . . . . . . . . . .............................. 44
4.3.1 AR Timer Description . . . . . . . . ........................................44
4.3.2 Timer Operating Modes . . .. . . . .. . . . .................................. 44
4.3.3 AR Timer Registers . . . . . . . . . . . . . . . . ................................. 48
4.4 A/D CONVERTER (ADC) . . ............................................... 50
4.4.1 Application Notes . . . ................................................50
5 SOFTWARE . . . . . . . . . . . . . . . . . ............................................... 52
5.1 ST6 ARCHITECTURE . ................................................... 52
5.2 ADDRESSING MODES . . . . . . . . . . . . . . . . . .................................. 52
5.3 INSTRUCTION SET . . . . . . . ............................................... 53
6 ELECTRICAL CHARACTERISTICS . .. . . . . . . . . . . . . . .............................. 58
6.1 ABSOLUTE MAXIMUM RATINGS . . . ........................................58
6.2 RECOMMENDED OPERATING CONDITIONS . . . .............................. 59
6.3 DC ELECTRICAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . ...........60
6.4 AC ELECTRICAL CHARACTERISTICS . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . 61
6.5 A/D CONVERTERCHARACTERISTICS . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 62
6.6 TIMER CHARACTERISTICS . . . . ........................................... 62
6.7 SPI CHARACTERISTICS . . ...............................................62
6.8 ARTIMER ELECTRICAL CHARACTERISTICS . . . . . . ........................... 62
7 GENERAL INFORMATION . . .. . . . . . . ...........................................68
7.1 PACKAGE MECHANICALDATA . . . . . . . . . . . . . . . . . ........................... 68
7.2 ORDERING INFORMATION . . . . . . . . . . . . . .................................. 70
ST62P52C/ST62P62C . . . . ............................71
1 GENERAL DESCRIPTION . .. . . . ............................................... 72
1.1 INTRODUCTION . . . . . .. . . . . . . ........................................... 72
1.2 ORDERING INFORMATION . . . . . . . . . . . . . .................................. 72
1.2.1 Transfer of Customer Code . . . . . . . . . . ................................. 72
1.2.2 Listing Generation and Verification . . . . ................................. 72
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Page
ST6252C/ST6262B . . . . ..............................75
1 GENERAL DESCRIPTION . .. . . . ............................................... 76
1.1 INTRODUCTION . . . . . .. . . . . . . ........................................... 76
1.2 ROM READOUT PROTECTION .. . . . .. . . . . . ................................76
1.3 ORDERING INFORMATION . . . . . . . . . . . . . .................................. 78
1.3.1 Transfer of Customer Code . . . . . . . . . . ................................. 78
1.3.2 Listing Generation and Verification . . . . ................................. 78
1
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ST62T52C ST62T62C/E62C
1 GENERAL DESCRIPTION
1.1 INTRODUCTION
The ST62T52C and ST62T62C devicesis lowcost members of theST62xx 8-bitHCMOSfamily ofmi­crocontrollers, which is targeted at low to medium complexity applications. All ST62xx devices are based on a building block approach: a common core issurroundedby a numberof on-chip periph­erals.
The ST62E62C isthe erasable EPROM version of the ST62T62C device, which may be used to em­ulate the ST62T52C and ST62T62C devices as well as the ST6252C and ST6262B ROMdevices.
OTP and EPROM devices are functionally identi­cal. The ROM basedversions offer the same func­tionality selecting as ROM options the options de-
fined 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 choicein a wide range of applications where frequent code changes, multiple code versions or last minute programmability are required.
These compact low-cost devices feature a Timer comprising an 8-bit counter and a 7-bit program­mable prescaler, an 8-bit Auto-Reload Timer, EEPROM data capability (except ST62T52C), an 8-bit A/D Converter with4 analoginputsanda Dig­ital Watchdog timer, making them well suited for a wide range of automotive, appliance and industrial applications.
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
PA4..PA5/ Ain
PB0, PB2..PB3 / 30 mA Sink
V
DDVSS
OSCin OSCout RESET
WATCHDOG
MEMORY
PB6 / ARTimin / 20 mA Sink
PORT C PC2..PC3 / Ain
AUTORELOAD
TIMER
PB7 / ARTimout/ 20 mA Sink
128 Bytes
1836 bytes OTP
(ST62T52C, T62C)
1836 bytes EPROM
(ST62E62C)
DATA EEPROM
64 Bytes
(ST62T62C/E62C)
4
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ST62T52C ST62T62C/E62C
1.2 PIN DESCRIPTIONS VDDand VSS. 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 tothe 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 re­start themicrocontroller.
TEST/VPP. TheTEST 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 programmingMode is entered.
NMI. TheNMI pin provides the capability for asyn­chronous interruption,byapplying an external non maskable interrupt to the MCU. The NMI input is falling edge sensitive. It is providedwith anon-chip pullup resistor (if option has been enabled), and Schmitt triggercharacteristics.
PA4-PA5. These 2 lines are organized as one I/O port (A). Each line may be configured under soft­ware controlas inputs withor without internal pull­up resistors, interrupt generating inputs with pull­up resistors, open-drain or push-pulloutputs, ana­log inputs for the A/D converter.
PB0, PB2-PB3, PB6-PB7. These 5 lines are or­ganized as one I/O port (B).Each linemaybe con­figured under software control as inputs with or without internal pull-up resistors, interrupt generat­ing inputs with pull-up resistors, open-drain or push-pull outputs. PB6/ARTIMin and PB7/ARTI-
Mout are either Port B I/O bits or the Input and Output pins of the ARTimer. Reset state of PB2-PB3pins canbedefinedbyop­tion either with pull-up or high impedance.
PB0, PB2-PB3, PB6-PB7 scan also sink30mA for direct LED driving.
PC2-PC3. These 2 lines are organized 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.
Figure 2. ST62T52C, E62C and T62C Pin Configuration
1 2 3 4 5 6 7 89
10
11
12
13
14
15
16
PB0
V
PP
/TEST
PB2
PB3
V
DD
ARTIMin/PB6
PC2/Ain
PC3/Ain
PA5/Ain PA4/Ain
ARTIMout/PB7
V
SS
NMI
RESET
OSCout
OSCin
5
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ST62T52C ST62T62C/E62C
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 thesethreememory spaces is described in the following paragraphs.
Briefly, Program space contains user program code in OTP and user vectors; Data space con­tains user data in RAM and in OTP, and Stack space accommodates six levels of stack for sub­routine and interrupt service routine nesting.
Figure 3. Memory Addressing Diagram
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
6
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ST62T52C ST62T62C/E62C
MEMORY MAP(Cont’d)
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 viathe12-bit ProgramCounter register (PC register).
1.3.2.1 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: Oncethe Readout Protection is activated, it is no longer possible, even for STMicroelectronics, to gain access to the OTP contents. Returned parts with aprotectionset can therefore not be ac­cepted.
Figure 4. ST62T52C/T62C Program
Memory Map
0000h
RESERVED
*
USER
PROGRAM MEMORY
(OTP/EPROM)
1836 BYTES
0F9Fh 0FA0h 0FEFh 0FF0h 0FF7h 0FF8h
0FFBh 0FFCh 0FFDh
0FFEh
0FFFh
RESERVED
*
RESERVED
INTERRUPT VECTORS
NMI VECTOR
USER RESET VECTOR
(*) Reserved areas should be filled with 0FFh
0880h
087Fh
7
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ST62T52C ST62T62C/E62C
MEMORY MAP(Cont’d)
1.3.3 Data Space
Data Spaceaccommodates all the datanecessary for processingthe 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 OTP/EPROM.
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 OTP/EPROM.
1.3.3.2 Data RAM/EEPROM
In ST62T52C, T62C and ST62E62C 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/Oport registers, the peripheral data and control registers, the interrupt option register and theDataROM Window register (DRW register).
Additional RAM and EEPROM pages can also be addressed using banks of 64 bytes located be­tween addresses00h 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 wellas the current program counter contents.
Table 1. Additional RAM / EEPROM Banks
Table 2. ST62T52C, T62C and ST62E62C Data
Memory Space
Device RAM EEPROM
ST62T52C 1 x 64 bytes ­ST62T62C 1 x 64 bytes 1 x 64bytes
RAM / EEPROM banks
000h
03Fh
DATA ROM WINDOW AREA
040h
07Fh X REGISTER 080h Y REGISTER 081h V REGISTER 082h
W REGISTER 083h
DATA RAM 60 BYTES
084h
0BFh
PORT A DATA REGISTER 0C0h PORT B DATA REGISTER 0C1h
PORT C DATA REGISTER 0C2h
RESERVED 0C3h PORT A DIRECTION REGISTER 0C4h PORT B DIRECTION REGISTER 0C5h PORT C DIRECTIONREGISTER 0C6h
RESERVED 0C7h
INTERRUPT OPTIONREGISTER 0C8h*
DATA ROM WINDOW REGISTER 0C9h*
RESERVED
0CAh
0CBh PORT A OPTION REGISTER 0CCh PORT B OPTION REGISTER 0CDh PORT C OPTION REGISTER 0CEh
RESERVED 0CFh
A/D DATA REGISTER 0D0h
A/D CONTROL REGISTER 0D1h
TIMER PRESCALERREGISTER 0D2h
TIMER COUNTERREGISTER 0D3h
TIMER STATUS CONTROL REGISTER 0D4h
AR TIMER MODE CONTROL REGISTER 0D5h AR TIMERSTATUS/CONTROLREGISTER1 0D6h AR TIMERSTATUS/CONTROLREGISTER2 0D7h
WATCHDOG REGISTER 0D8h
AR TIMERRELOAD/CAPTURE REGISTER 0D9h
AR TIMERCOMPARE REGISTER 0DAh
AR TIMER LOAD REGISTER 0DBh
OSCILLATOR CONTROL REGISTER 0DCh*
MISCELLANEOUS 0DDh
RESERVED
0DEh 0E7h
DATA RAM/EEPROM REGISTER 0E8h*
RESERVED 0E9h
EEPROMCONTROL REGISTER 0EAh
RESERVED
0EBh 0FEh
ACCUMULATOR 0FFh
* WRITE ONLY REGISTER
8
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ST62T52C ST62T62C/E62C
MEMORY MAP(Cont’d)
1.3.5 Data Window Register (DWR)
TheDataread-only memorywindowislocatedfrom address 0040h toaddress 007Fh in Data space. It allows directreadingof64 consecutive bytes locat­ed anywhere in program memory, between ad­dress 0000h and 0FFFh (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 pro­gram memoryby writingtheappropriatecodeinthe Data Window Register (DWR).
The DWR can beaddressedlike anyRAMlocation in theData Space, it is howevera write-only regis­ter andtherefore cannotbe accessedusingsingle­bit operations. This register is used to position the 64-byte read-onlydata 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 registeraddress given in the instruction (as least significant bits) and the content of the DWR register (asmost significant bits),as illustrat­ed in Figure 5 below. 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 to the first access to the Data read­only memory window area.
Data Window Register (DWR)
Address: 0C9h Write Only
Bits 6, 7= Not used. Bit 5-0 = 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 dataread-only memory space.
Caution:
This register is undefined on reset. Nei­ther read nor single bit instructionsmay be used 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 saveand thenrestoretheregister’s previous contents. If it is impossible to avoid writ­ing to the DWRduring 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 writeto theimage 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
- - 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
VR01573C
12
1
0
DATA SPACE ADDRESS
:
:
59h
000
01001
11
Example:
(DWR)
DWR=28h
1100000001
ROM
ADDRESS:A19h
11
13
0
1
9
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ST62T52C ST62T62C/E62C
MEMORY MAP(Cont’d)
1.3.6 Data RAM/EEPROM Bank Register (DRBR)
Address: E8h — Write only
Bit 7-5= These bits are not used Bit 4 - DRBR4. This bit, when set, selects RAM
Page 2. Bit 3-1. Not used Bit 0. DRBR0. This bit, when set, selects EEP-
ROM page 0. The selection of the bank is made byprogramming
the Data RAM Bank Switch register (DRBR regis­ter) located at address E8h of the Data Space ac­cording to Table 1.No more than one bank should be setat a time.
The DRBR register can be addressed like a RAM Data Space at the address E8h; nevertheless it is a write only register that cannot be accessed with single-bit operations. This register isused toselect the desired 64-byte RAM bank of the Data Space. The bank number 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 registeris 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 informa-
tion. The DRBR register is not modified when an interrupt or a subroutine occurs.
Notes : Care is requiredwhen 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 thisregister 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.
Care must also be taken not to change the E
PROM page (when available) when the parallel writing mode is set for theE PROM, as defined in EECTL register.
Table 3. Data RAM Bank Register Set-up
70
---
DRBR
4
---
DRBR
0
DRBR ST62T52C ST62T62C
00 None None 01 Not available EEPROM page 0 02 Not Available Not Available 08 Not available Not available
10h RAM Page 2 RAM Page 2
other Reserved Reserved
10
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ST62T52C ST62T62C/E62C
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 spacefrom 00h to3Fh ispagedas described in Table 4 . EEPROM locations are accessed di­rectly by addressing these paged sections of data space.
The EEPROM does notrequire dedicated instruc­tions forread orwrite access.Onceselectedviathe Data RAM Bank Register, the active EEPROM page is controlledby theEEPROM Control Regis­ter (EECTL),which is described below.
Bit E20FFoftheEECTL registermust bereset prior to any write or read access to the EEPROM. If no bank hasbeenselected, orif E2OFFisset,any ac­cess is meaningless.
Programming must be enabled by setting the E2ENA bitof the EECTL register.
The E2BUSY bit 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 E2OFFand E2BUSY arereset, an EEP­ROM location is readjust like any other data loca­tion, alsoin 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 andpower consumption advantages, the latter being particularly important in battery powered circuits).
General Notes: Data should be writtendirectly to the intended ad-
dress in EEPROM space.There is no buffer mem­ory between data RAM andthe 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 required whendealing 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, animage of the register must be saved in a RAM location, and each time the program writes to EECTL it must also write to 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 4. Row Arrangement for Parallel Writing of EEPROM Locations
Note: The EEPROM is disabled as soon as STOP instruction is executed in order to achieve the lowest
power-consumption.
Dataspace addresses. Banks 0 and 1.
Byte 0 1234567 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 to8 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.
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ST62T52C ST62T62C/E62C
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 addressis latched,the MCUcanonly “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 allor inpart ofthe ROW. Setting E2PAR1 will modify the EEPROM regis­ters corresponding to the ROW latches accessed after E2PAR2. For example, if the software sets E2PAR2 andaccesses 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 setthe E2PAR2bit betweentwo parallel pro­gramming cycles. Note that if the user tries to set E2PAR1 while E2PAR2 is not set, there will be no programming cycleand the E2PAR1 bit will be un­affected. Consequently, the E2PAR1 bit cannot be set if E2ENA is low.The E2PAR1 bit can be setby the user, only if the E2ENA and E2PAR2 bits are also set.
Notes: The EEPROM page shall not be changed through the DRBR register when the E2PAR2 bit is set.
EEPROM Control Register (EECTL)
Address: EAh Read/Write Reset status: 00h
Bit 7 =D7:
Unused.
Bit6=E2OFF:
Stand-byEnableBit.
WRITE ONLY. Ifthisbitis settheEEPROM isdisabled(anyaccess will bemeaningless) andthepower consumptionof the EEPROM is reduced to its lowest value.
Bit 5-4 = D5-D4:
Reserved.
MUST bekept reset.
Bit 3 =E2PAR1:
Parallel Start Bit.
WRITE ONLY. OnceinParallelMode,as soonastheusersoftware sets the E2PAR1 bit, parallel writing of the 8 adja­cent registers will start. Thisbitisinternally reset at the end of the programming procedure. Note that less than 8 bytescan bewritten if required, the un­defined bytes being unaffected by the parallelpro­grammingcycle;thisisexplainedingreater detailin the Additional Notes on Parallel Mode overleaf.
Bit 2 = E2PAR2:
Parallel Mode En. Bit.
WRITE ONLY. This bitmust be set by 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 bytesareconsidered as a row, whose address lines A7, A6, A5, A4, A3 are fixed while A2, A1 and A0 arethechangingbits, as illustrated in Table 4. 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 userprogram should test it before any EEPROM read orwriteoperation;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
E2O
FF
D5 D4
E2PAR1E2PAR2E2BUSYE2E
NA
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ST62T52C ST62T62C/E62C
1.4 PROGRAMMING MODES
1.4.1 Option Bytes
The two Option Bytes allow configurationcapabili­ty to the MCUs. Option byte’s content is automati­cally read, and the selected options enabled,when the chipreset 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 modeofthepro­grammer.
The option bytes are located in a non-user map. No address has to bespecified.
EPROM Code Option Byte (LSB)
EPROM Code Option Byte (MSB)
D15-D13. Reserved. Must becleared. ADC SYNCHRO.When set, an A/D conversion is
started upon WAIT instruction execution, in order to reduce supply noise. When this bit is low, an A/D conversion isstartedassoon astheSTAbit of the A/D Converter Control Registeris set.
D11. Reserved,must be set to one. D10. Reserved,must be cleared. NMI PULL.
NMI Pull-Up
. This bit must be set high to configure the NMI pin with a pull-up resistor. When itis low, no pull-up is provided.
LVD.
LVD RESETenable.
When this bitisset,safe RESET is performed by MCU when the supply voltage is too low. When this bit is cleared, only power-on reset or external RESET are active.
PROTECT.
Readout Protection.
Thisbitallows the protection of the softwarecontents against piracy. When the bit PROTECT is sethigh, readout of the OTP contents is prevented by hardware.. When this bit is low, the user program can be read.
EXTCNTL.
External STOP MODE control.
. When EXTCNTL is high, STOP mode is available with watchdog active by setting NMI pin to one. When
EXTCNTL is low, STOP mode is not available with the watchdog active.
PB2-3 PULL. When set this bit removespull-up at reset on PB2-PB3 pins. When cleared PB2-PB3 pins have an internal pull-up resistor at reset.
D4. Reserved.Must be cleared to 0. WDACT. This bit controls the watchdog activation.
When it is high, hardware activation is selected. The software activation is selected when WDACT is low.
DELAY. This bit enables the selection of the delay internally generated after the internal reset (exter­nal pin, LVD, or watchdog activated) is released. When DELAY is low, the delay is 2048 cycles of the oscillator, it is of 32768 cycles when DELAY is high.
OSCIL.
Oscillator selection
. When this bit is low, the oscillator must be controlled by a quartz crys­tal, a ceramic resonator or an external frequency. When it is high, the oscillator must be controlled by an RC network, with only the resistor having to be externally provided.
OSGEN.
Oscillator Safe Guard
. 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 ST62T62C is described in the User Manual of the EPROM Programming Board.
The MCUs can be programmed with the ST62E6xB EPROM programming tools available from STMicroelectronics.
Table 5. ST62T52C/T62C Program MemoryMap
Note: OTP/EPROM devices can be programmed
with the development tools available from STMi­croelectronics (ST62E6X-EPB or ST626X-KIT).
70
PRO­TECT
EXTC-
NTL
PB2-3
PULL
- WDACT
DE-
LAY
OSCIL OSGEN
15 8
---
ADC
SYNCHRO
--
NMI
PULL
LVD
Device Address Description
0000h-087Fh
0880h-0F9Fh
0FA0h-0FEFh
0FF0h-0FF7h 0FF8h-0FFBh 0FFCh-0FFDh 0FFEh-0FFFh
Reserved
User ROM
Reserved
Interrupt Vectors
Reserved
NMI Interrupt Vector
Reset Vector
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ST62T52C ST62T62C/E62C
PROGRAMMING MODES (Cont’d)
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 theapplication software or through an ex-
ternal programmer. Any STMicroelectronics tool used for the program memory (OTP/EPROM) can also be used to program the EEPROM data mem­ory.
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ST62T52C ST62T62C/E62C
2 CENTRAL PROCESSING UNIT
2.1 INTRODUCTION
The CPUCoreofST6 devicesisindependentof the 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 thecore islinked tothededicated 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 as a RAM location at address 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 canalso beac­cessed with the direct, shortdirect, orbit direct ad­dressing modes. Accordingly, the ST6 instruction set can usethe indirect registers asanyother 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 locationsat 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 6ST6 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 DATASPACE (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
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ST62T52C ST62T62C/E62C
CPU REGISTERS (Cont’d)
However, if theprogram space contains morethan 4096 bytes, the additional memory in program space can be addressed by using the Program Bank Switch register.
The PC value is incrementedafter reading the ad­dress of the current instruction. Toexecuterelative 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 programcounter can be changedin the following ways:
- JP (Jump) instructionPC=Jump address
- CALL instructionPC= Call address
- Relative Branch Instruction.PC= PC +/- offset
- InterruptPC=Interrupt vector
- ResetPC= Reset vector
- RET& RETI instructionsPC= Pop (stack)
- NormalinstructionPC= PC + 1 Flags (C, Z). TheST6 CPU includes three pairsof
flags (CarryandZero), each pair being 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), anda third pairisused 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 andthus 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 inthe rotate left instruction.
The Zero flag isset if the result of the last arithme­tic or logical operation was equal to zero; other­wise itis cleared.
Switching between the three sets of flags is per­formed automatically when an NMI, an interruptor
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 asubroutine call (orinter­rupt request)occurs, the contentsof eachlevelare 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 (RET or 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 morethan 6 nested calls orinterrupts 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 orRETI isexecuted. In this case the nextinstruction will be executed.
Figure 7ST6 CPU Programming Mode
l
SHORT
DIRECT
ADDRESSING
MODE
VREGISTER
W REGISTER
PROGRAMCOUNTER
SIX LEVELS
STACKREGISTER
CZNORMAL FLAGS
INTERRUPTFLAGS
NMI FLAGS
INDEX
REGISTER
VA000 4 23
b7
b7
b7
b7
b7
b0
b0
b0
b0
b0
b0b11
ACCUM ULATO R
Y REG. PO INTER
X REG. PO INTER
CZ
CZ
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ST62T52C ST62T62C/E62C
3 CLOCKS, RESET, INTERRUPTS AND POWERSAVING MODES
3.1 CLOCK SYSTEM
The MCU features a Main Oscillatorwhich can be driven byan external clock, orused in conjunction with an AT-cut parallel resonant crystal or a suita­ble ceramic resonator, or with an external resistor (R
NET
). In addition, a Low FrequencyAuxiliary Os­cillator (LFAO)canbe switched in for security rea­sons, to reduce powerconsumption, orto 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 of VDD, inorder toguarantee correctoper­ation. These functions are illustrated in Figure 9., Figure 10., Figure 11. and Figure 12..
Figure 8.illustrates various possible oscillator con­figurations using anexternal crystal orceramicres­onator, an external clock input, anexternal resistor (R
NET
), or the lowest cost solution using only the LFAO. CL1anCL2shouldhave acapacitance inthe range 12 tST6_CLK1o 22 pF for an oscillator fre­quency in the 4-8 MHz range.
The internal MCU clock frequency (f
INT
) is divided by 12to drive the Timer,theA/D converter andthe Watchdog timer, and by 13 to drive the CPU core, as may be seen in Figure 11..
With an 8MHz oscillator frequency, thefastestma­chine cycle is therefore 1.625µs.
A machine cycleisthesmallest unit of timeneeded to executeanyoperation(for instance,to increment the Program Counter). An instruction may require two, four, or five machine cycles forexecution.
3.1.1 Main Oscillator
The oscillatorconfiguration maybe specifiedbyse­lecting the appropriate option. When the CRYS­TAL/RESONATOR option is selected, it must be usedwithaquartzcrystal,aceramicresonatororan externalsignalprovidedonthe OSCinpin.Whenthe RC NETWORKoptionisselected,thesystem clock is generated by an external resistor.
The main oscillator can be turned off (when the OSG ENABLED option isselected) by setting the OSCOFF bit of the ADC Control Register. The Low Frequency Auxiliary Oscillator isautomatical­ly started.
Figure 8. Oscillator Configurations
INTEGRATED CLOCK
CRYSTAL/RESONATOR option
OSG ENABLED option
OSC
in
OSC
out
C
L1n
C
L2
ST6xxx
CRYSTAL/RESONATOR CLOCK
CRYSTAL/RESONATOR option
OSC
in
OSC
out
ST6xxx
EXTERNAL CLOCK
CRYSTAL/RESONATOR option
NC
OSC
in
OSC
out
ST6xxx
NC
OSC
in
OSC
out
R
NET
ST6xxx
RC NETWORK
RC NETWORK option
NC
17
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ST62T52C ST62T62C/E62C
CLOCK SYSTEM (Cont’d)
Turning on the main oscillator is achieved by re­setting the OSCOFF bit of the A/DConverterCon­trol 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 softwareinstruction 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 anyexternal components.Lastly, itactsas a safetyoscillatorin case of main oscillator failure.
This oscillator is available when the OSG ENA­BLED option is selected. In this case, it automati­cally startsone of itsperiods after the first missing edge from the main oscillator, whateverthereason (main oscillatordefective, noclock circuitryprovid­ed, main oscillator switched off...).
User code,normal interrupts, WAIT and STOP in­structions, are processed as normal, at the re­duced f
LFAO
frequency.TheA/Dconverter accura­cy is decreased, since the internal frequency is be­low 1MHz.
At power on, the Low Frequency Auxiliary Oscilla­tor starts faster than the Main Oscillator. It there­fore feeds the on-chip counter generating the POR delay untilthe Main Oscillator runs.
The Low Frequency Auxiliary Oscillator is auto­matically switched off as soon as the main oscilla­tor starts.
ADCR
Address: 0D1h — Read/Write
Bit 7-3, 1-0= ADCR7-ADCR3, ADCR1-ADCR0:
ADC ControlRegister
. These bits are not used.
Bit 2 = OSCOFF. When low, thisbit enables main oscillator torun. The mainoscillator is switched off when OSCOFF is high.
3.1.3 Oscillator Safe Guard
The Oscillator Safe Guard (OSG) affordsdrastical­ly increasedoperational integrity in ST62xx devic­es. The OSG circuit provides three basic func-
tions: it filtersspikes from the oscillator lines which would result inover 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 consumptionortoprovide afixed 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 viewedas a filter whose cross-over frequency is device dependent.
Spikes on the oscillatorlinesresultinan effectively increased internal clock frequency.Inthe absence of an OSG circuit, this may lead to an over fre­quency for a given power supply voltage. The OSG filters out such spikes (as illustrated in Figure
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 in Figure 12.. When the OSG is enabled, the Low Frequency
Auxiliary Oscillator maybe accessed. This oscilla­tor starts operating after the first missing edge of the main oscillator (see Figure 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 OSG should beusedwherever possible
as it provides maximumsafety. Care must be tak­en, however, as it can increase power consump­tion and reduce the maximum operating frequency to f
OSG
.
Warning: Care has to be taken when using the OSG, as the internal frequency is defined between a minimum and amaximumvalue and is not accu­rate.
For precise timing measurements, it is not recom­mended to use the OSG and it should not be ena­bled in applications that use the SPI or the UART.
It should also be noted that power consumption in Stop mode is higher when the OSG is enabled (around 50µA at nominal conditions and room temperature).
70
ADCR7ADCR6ADCR5ADCR4ADCR3OSC
OFF
ADCR1ADCR
0
18
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ST62T52C ST62T62C/E62C
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 OSCinpin Noise from OSCin
Resulting Internal Frequency
Main
VR001933
Internal
Emergency
Oscillator
Frequency
Oscillator
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ST62T52C ST62T62C/E62C
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. When the OSG is disabled, operation in this area isguaranteedat the crystal frequency. When the OSGisenabled, 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 crystalfrequency. 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
1
2.5 3.6 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 (at 85°C)
GUARANTEED
IN THIS AREA
VR01807J
f
OSG
Min (at 125°C)
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ST62T52C ST62T62C/E62C
3.2 RESETS
The MCU can be reset in four ways: – by the external Reset input being pulled low; – by Power-onReset; – by the digital Watchdog peripheral timing out. – by LowVoltage Detection (LVD)
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 toreset the MCU internal state andensure a correct start-up procedure. The pin is active low and features a Schmitt trigger input. The internal Reset signalis 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 theoscillatoris running correctly (normal RUN or WAIT modes). The MCU is keptin 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 modeonly), theInputsandOutputsare 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 pinactivation 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 the RESET 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 by detecting around 2V a dynamic (rising edge) variation of the VDD Supply. 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 to a sufficient level, the oscillator starts to operate, whereupon aninternal delay is initiated, inorder to allow the oscillator to fully stabilize before execut­ing the first instruction. The initialization sequence
is executed immediately following the internal de­lay.
To ensure correct start-up, the user should take care that the VDD Supply is stabilized at a suffi­cient level for the chosen frequency (see recom­mended operation) before the reset signal is re­leased. In addition, supply rising must start from 0V.
As a consequence, the POR does not allow to su­pervise static, slowly rising, or falling, or noisy (presenting oscillation) VDD supplies.
An external RC network connected to the RESET pin, or the LVD reset can be used instead to get the best performances.
Figure 13. Reset and Interrupt Processing
INT LATCH CLEARED
NMI MASKSET
RESET
( IFPRESENT )
SELECT
NMI MODE FLAGS
IS RESETSTILL
PRESENT?
YES
PUT FFEH
ON ADDRESSBUS
FROM RESETLOCATIONS
FFE/FFF
NO
FETCH INSTRUCTION
LOAD PC
VA000427
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ST62T52C ST62T62C/E62C
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 LVD Reset
The on-chip Low Voltage Detector, selectable as user option, features static Reset when supply voltage is below a reference value. Thanks to this feature, external reset circuit can be removed while keeping the application safety. This SAFE RESET is effective as well in Power-on phase as in power supply drop with different reference val-
ues, allowing hysteresiseffect. Reference value in case of voltage drop has been set lower than the reference value for power-on in order to avoid any parasitic Reset when MCU start’s running and sinking current on the supply.
As long as the supply voltage is below the refer­ence value, there is a internal and static RESET command. The MCU can start only when the sup­ply voltage rises over the reference value. There­fore, only two operating mode exist for the MCU: RESET active below the voltage reference, and running mode over the voltage reference as shown on the Figure 14., that represents a power­up, power-down sequence.
Note: When the RESET state is controlled by one of the internal RESET sources (Low Voltage De­tector, Watchdog, Power on Reset), the RESET pin is tied to low logic level.
Figure 14. LVD Reset on Power-on and Power-down (Brown-out)
3.2.5 Application Notes
No external resistor is required between VDDand the Reset pin, thanks to the built-in pull-up device.
Direct external connection of the pin RESET to VDDmust be avoided in order to ensure safe be­haviour of the internal reset sources (AND.Wired structure).
RESET
RESET
VR02106A
time
V
Up
V
dn
V
DD
22
24/78
ST62T52C ST62T62C/E62C
RESETS (Cont’d)
3.2.6 MCU Initialization Sequence
When a reset occurs the stack is reset, the PC is loaded with the address of the Reset Vector (locat­ed in programROM starting at address 0FFEh). A jump tothe beginning oftheuser programmustbe coded at this address. Following a Reset, the In­terrupt flag is automatically set, so that the CPU is in NonMaskable Interrupt mode; this prevents the initialisation routinefrom being interrupted. The in­itialisation routine should therefore be terminated by a RETI instruction, in order to revert to normal mode and enable interrupts. If nopendinginterrupt is present at the endof theinitialisationroutine,the MCU will continue by processing the instruction immediately following the RETIinstruction.If,how­ever, a pending interrupt is present, it will be serv­iced.
Figure 15. Reset and Interrupt Processing
Figure 16. Reset Block Diagram
RESET
RESET
VECTOR
JP
JP:2 BYTES/4 CYCLES
RETI
RETI: 1 BYTE/2 CYCLES
INITIALIZATION
ROUTINE
VA00181
V
DD
RESET
R
PU
R
ESD
1)
POWER
WATCHDOGRESET
CK
COUNTER
RESET
ST6 INTERNAL RESET
f
OSC
RESET
ON RESET
LVD RESET
VR02107A
AND. Wired
1) Resistive ESD protection. Value not guaranteed.
23
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