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

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

■8 MHz Maximum Clock Frequency

■-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: 128 bytes

■Data EEPROM: 64 bytes (none on ST62T52C)

■User Programmable Options

■9 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

■5 I/O lines can sink up to 30mA to drive LEDs or TRIACs directly

■8-bit Timer/Counter with 7-bit programmable prescaler

PDIP16

PSO16

■8-bit Auto-reload Timer with 7-bit programmable prescaler (AR Timer)

■Digital Watchdog

■Oscillator Safe Guard

■Low Voltage Detector for Safe Reset

■8-bit A/D Converter with 4 analog inputs

■On-chip Clock oscillator can be driven by Quartz Crystal Ceramic resonator or RC network

■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	OTP	EEPROM
		(Bytes)	(Bytes)
	ST62T52C		1836	-
	ST62T62C		1836	64
	ST62E62C	1836		64

SSOP16

CDIP16W

(See end of Datasheet for Ordering Information)

Rev. 2.7

November 1999

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Table of Contents

Document

Page

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 POWER SAVING 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 CONVERTER CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 6.6 TIMER CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 6.7 SPI CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 6.8 ARTIMER ELECTRICAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

7 GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

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

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1 GENERAL DESCRIPTION

1.1 INTRODUCTION

The ST62T52C and ST62T62C devices is 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 common core is surrounded by a number of on-chip peripherals.

The ST62E62C is the 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 ROM devices.

OTP and EPROM devices are functionally identical. The ROM based versions offer the same functionality selecting as ROM options the options de-

Figure 1. Block Diagram

TEST/VPP

NMI

TEST

INTERRUPT

PROGRAM

MEMORY

1836 byte s OTP (ST62T52C, T62C)

1836 byte s EPROM (ST62E62C)

PC

STACK LEVEL 1 STACK LEVEL 2 STACK LEVEL 3 STACK LEVEL 4 STACK LEVEL 5 STACK LEVEL 6

8-BIT

A/D CONVERTER

DATA ROM

USER

SELECTABLE

DATA RAM

128 Bytes

DATA EEPROM

64 Bytes

(ST62T62C/E6 2C)

8 BIT CORE

POWER OSCILLATOR RESET SUPPLY

VDD VSS OSCin OSCout RESET

ST62T52C ST62T62C/E62C

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 choice in 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 with 4 analog inputs and a Digital Watchdog timer, making them well suited for a wide range of automotive, appliance and industrial applications.

PORT A

PA4..PA 5 / Ain

PB0, PB2..PB3 / 30 mA Sink PORT B PB6 / ARTimin / 20 mA Sink PB7 / ARTimout / 20 mA Sink

PORT C

PC2..PC3 / Ain

AUTORELOAD

TIMER

TIMER

DIGITAL

WATCHD OG

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ST62T52C ST62T62C/E62C

1.2 PIN DESCRIPTIONS

VDD and VSS. Power is supplied to the MCU via these two pins. VDD is the power connection and VSS is 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 restart the microcontroller.

TEST/VPP. The TEST must be held at VSS for normal 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. It is provided with an on-chip pullup resistor (if option has been enabled), and Schmitt trigger characteristics.

PA4-PA5. These 2 lines are organized 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, analog inputs for the A/D converter.

PB0, PB2-PB3, PB6-PB7. These 5 lines are organized as one I/O port (B). Each line may be 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-PB3 pins can be defined by option either with pull-up or high impedance.

PB0, PB2-PB3, PB6-PB7 scan also sink 30mA 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

PB0	1	16	PC2/Ain
VPP/TEST	2	15	PC3/Ain
PB2	3	14	NMI
PB3	4	13	RESET
ARTIMin/PB6	5	12	OSCout
ARTIMout/PB7	6	11	OSCin
VDD	7	10	PA5/Ain
VSS	8	9	PA4/Ain

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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.

Figure 3. Memory Addressing Diagram

PROGRAM SPACE

0000h

0-63

PROGRAM

MEMORY

0FF0h

INTERRUPT &

RESET VECTORS

0FFFh

ST62T52C ST62T62C/E62C

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.

	DATA SPACE
000h
	RAM / EEPROM
	BANKING AREA
03Fh
040h
	DATA READ-ONLY
	MEMORY WINDOW
07Fh
080h	X REGISTER
081h	Y REGISTER
082h	V REGISTER
083h	W REGISTER
084h	RAM
0C0h	DATA READ-ONLY
	MEMORY
	WINDOW SELECT
	DATA RAM
	BANK SELECT
0FFh	ACCUMULATOR

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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 via the 12-bit Program Counter 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: Once the Readout Protection is activated, it is no longer possible, even for STMicroelectronics, to gain access to the OTP contents. Returned parts with a protection set can therefore not be accepted.

Figure 4. ST62T52C/T62C Program

Memory Map

0000h

RESERVED*

087Fh

0880h

		USER
		PROGRAM MEMORY
		1836 BYTES
		(OTP/EPROM)
	0F9Fh
	0FA0h	RESERVED*
	0FEFh
	0FF0h	INTERRUPT VECTORS
	0FF7h
	0FF8h	RESERVED
	0FFBh
	0FFCh	NMI VECTOR
	0FFDh
	0FFEh	USER RESET VECTOR
	0FFFh

(*) Reserved areas should be filled with 0FFh

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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 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/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 1. Additional RAM / EEPROM Banks

Device	RAM	EEPROM
ST62T52C	1 x 64 bytes	-
ST62T62C	1 x 64 bytes	1 x 64 bytes

ST62T52C ST62T62C/E62C

Table 2. ST62T52C, T62C and ST62E62C Data

Memory Space

000h

RAM / EEPROM banks

		03Fh
		040h
	DATA ROM WINDOW AREA
		07Fh
	X REGISTER	080h
	Y REGISTER	081h
	V REGISTER	082h
	W REGISTER	083h
	DATA RAM 60 BYTES	084h
		0BFh
	PORT A DATA REGISTE R	0C0h
	PORT B DATA REGISTE R	0C1h
	PORT C DATA REGISTER	0C2h
	RESERVED	0C3h
	PORT A DIRECTION REGISTER	0C4h
	PORT B DIRECTION REGISTER	0C5h
	PORT C DIRECTI ON REGISTER	0C6h
	RESERVED	0C7h
	INTERRUPT OPTION REGISTE R	0C8h*
	DATA ROM WINDOW REGISTER	0C9h*
	RESERVED	0CAh
		0CBh
	PORT A OPTION REGISTER	0CCh
	PORT B OPTION REGISTER	0CDh
	PORT C OPTION REGISTE R	0CEh
	RESERVED	0CFh
	A/D DATA REGISTER	0D0h
	A/D CONTROL REGISTER	0D1h
	TIMER PRESCALER REGISTER	0D2h
	TIMER COUNTER REGISTE R	0D3h
	TIMER STATUS CONTROL REGISTER	0D4h
	AR TIMER MODE CONTROL REGISTER	0D5h
	AR TIMER STATUS/CONT ROL REGISTE R1	0D6h
	AR TIMER STATUS/CONT ROL REGISTE R2	0D7h
	WATCHDOG REGISTER	0D8h
	AR TIMER RELOAD/CAPTU RE REGISTE R	0D9h
	AR TIMER COMPARE REGISTER	0DAh
	AR TIMER LOAD REGISTER	0DBh
	OSCILLATOR CONTROL REGISTER	0DCh*
	MISCELLANEOUS	0DDh
	RESERVED	0DEh
		0E7h
	DATA RAM/EEP ROM REGISTER	0E8h*
	RESERVED	0E9h
	EEPROM CONTROL REGISTER	0EAh
	RESERVED	0EBh
		0FEh
	ACCUMULATOR	0FFh

* WRITE ONLY REGISTER

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ST62T52C ST62T62C/E62C

MEMORY MAP (Cont'd)

1.3.5 Data Window Register (DWR)

The Data read-only memory window is located from 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 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 memory by writing the appropriate code in the Data Window Register (DWR).

The DWR can 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 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 Ð Write Only

7

0

-- DWR5 DWR4 DWR3 DWR2 DWR1 DWR0

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 data read-only memory space.

Caution: This register is undefined on reset. Neither read nor single bit instructions may 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 save and then restore the register's previous contents. If it is impossible to avoid writing to the DWR 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

DATA ROM	13	12	11 10 9			8	7	6	5	4	3	2	1	0 PROGRAM SPACE ADDRESS
															READ
WINDOW REGISTER 7		6	5	4	3	2	1	0
CONTENTS									5	4	3	2	1	0	DATA SPACE ADDRESS
(DWR)
															:
							0	1							40h-7Fh
															IN INSTRUCTION
Example:
DWR=28h			1	0	1	0	0	0							DATA SPACE ADDRESS
							0	1	0	1	1	0	0	1
															:
															59h
ROM			1	0	1	0	0	0	0	1	1	0	0	1
ADDRESS:A19h
															VR01573C

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MEMORY MAP (Cont'd)

1.3.6 Data RAM/EEPROM Bank Register (DRBR)

	Address: E8h		Ð	Write only
	7							0
	-	-	-	DRBR	-	-	-	DRBR
				4				0

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 EEPROM page 0.

The selection of the bank is made by programming 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 set at 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 is used to select 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 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 informa-

ST62T52C ST62T62C/E62C

tion. The DRBR register is not modified when an interrupt or a subroutine occurs.

Notes :

Care is required 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.

Care must also be taken not to change the E PROM page (when available) when the parallel writing mode is set for the E PROM, as defined in EECTL register.

Table 3. Data RAM Bank Register Set-up

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

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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 space from 00h to 3Fh is paged as described in Table 4 . EEPROM locations are accessed directly by addressing these paged sections of data space.

The EEPROM does not require dedicated instructions for read or write access. Once selected via the Data RAM Bank Register, the active EEPROM page is controlled by the EEPROM Control Register (EECTL), which is described below.

Bit E20FF of the EECTL register must be reset prior to any write or read access to the EEPROM. If no bank has been selected, or if E2OFF is set, any access is meaningless.

Programming must be enabled by setting the E2ENA bit of the EECTL register.

The E2BUSY bit of the EECTL register is set when 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 address in EEPROM space. There is no buffer memory between data RAM and the EEPROM space.

When the EEPROM is busy (E2BUSY = ª1º) 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 when 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 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

								Dataspace
								addresses.
								Banks 0 and 1.
Byte	0	1	2	3	4	5	6	7
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.

Note: The EEPROM is disabled as soon as STOP instruction is executed in order to achieve the lowest power-consumption.

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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 address is latched, the MCU can only ªseeº 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 the E2PAR1 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.

Notes: The EEPROM page shall not be changed through the DRBR register when the E2PAR2 bit is set.

EEPROM Control Register (EECTL)

Address: EAh Ð Read/Write

Reset status: 00h

	7							0
	D7	E2O	D5	D4	E2PA	E2PA	E2BU	E2E
		FF			R1	R2	SY	NA

Bit 7 = D7: Unused.

Bit 6 = E2OFF: Stand-by Enable Bit. WRITE ONLY. If this bit is set the EEPROM is disabled (any access will be meaningless) and the power consumption 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. Once in Parallel Mode, as soon as the user software sets the E2PAR1 bit, parallel writing of the 8 adjacent registers will start. This bit is internally reset at the end of the programming procedure. Note that less than 8 bytes can be written if required, 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 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 bytes are considered as a row, whose address lines A7, A6, A5, A4, A3 are fixed while A2, A1 and A0 are the changing bits, 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 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.

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ST62T52C ST62T62C/E62C

1.4 PROGRAMMING MODES

1.4.1 Option Bytes

The two Option Bytes allow 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 of the programmer.

The option bytes are located in a non-user map. No address has to be specified.

EPROM Code Option Byte (LSB)

	7					0
	PRO-	EXTC-	PB2-3	- WDACT	DE-	OSCIL OSGEN
	TECT	NTL	PULL		LAY

EPROM Code Option Byte (MSB)

	15							8
	-	-	-	ADC	-	-	NMI	LVD
				SYNCHRO			PULL

D15-D13. Reserved. Must be cleared.

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 is started as soon as the STA bit of the A/D Converter Control Register is 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 it is low, no pull-up is provided.

LVD. LVD RESET enable.When this bit is set, 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. 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.. 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 removes pull-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/VPP pin. 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 Memory Map

Device Address	Descriptio n
0000h-087Fh	Reserved
0880h-0F9Fh	User ROM
0FA0h-0FEFh	Reserved
0FF0h-0FF7h	Interrupt Vectors
0FF8h-0FFBh	Reserved
0FFCh-0FFDh	NMI Interrupt Vector
0FFEh-0FFFh	Reset Vector

Note: OTP/EPROM devices can be programmed with the development tools available from STMicroelectronics (ST62E6X-EPB or ST626X-KIT).

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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 the application software or through an ex-

ST62T52C ST62T62C/E62C

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 CPU Core of ST6 devices is independent of 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 the core is linked to the dedicated on-chip peripherals via the serial data bus and indirectly, for interrupt purposes, through the control registers.

2.2 CPU REGISTERS

The ST6 Family CPU corefeatures six registers and 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.

Figure 6ST6 Core Block Diagram

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, short direct, 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.

		0,01 TO 8MHz
	RESET	OSCin	OSCout
			INTERRUPTS
		CONTROLLER
					DATA SPACE
		FLAG	CONTROL
	OPCODE		SIGNALS		DATA
		VALUES	ADDRESS /READ LINE
		2			RAM/EEPR OM
PROGRAM					DATA
ROM/EPROM			ADDRESS
				256	ROM/EPROM
			DECODER
		A-DATA B-DATA			DEDICAT IONS
					ACCUMULATOR
12	Program Counter
	and	FLAGS
	6 LAYER STACK		ALU

RESULTS TO DATA SPACE (WRITE LINE)

VR01811

16/78

CPU REGISTERS (Cont'd)

However, if the 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

-ResetPC= 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 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), 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

ST62T52C ST62T62C/E62C

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 (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 ªdeepestº 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 7ST6 CPU Programming Mode

l

	INDEX	b7	X REG. POINTER		b0	SHORT
	REGISTER
		b7	Y REG. POINTER		b0	DIRECT
						ADDRESSING
		b7	V REGISTER		b0	MODE
		b7	W REGISTER		b0
		b7	ACCUM ULATO R		b0
	b11	PROGRAM COUNTER			b0
		SIX LEVELS
		STACK REGISTER
	NORMAL FLAGS			C	Z
	INTERRUPT FLAGS			C	Z
	NMI FLAGS			C	Z
						VA000423

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ST62T52C ST62T62C/E62C

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, or with an external resistor

(RNET). In addition, a Low Frequency Auxiliary Oscillator (LFAO) can be switched in for security rea-

sons, to reduce power consumption, or to offer the benefits of a back-up clock system.

Figure 8. Oscillator Configurations

CRYSTAL/RES ONATOR CLOCK

CRYSTAL/RESON ATOR option

ST6xxx

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 (fINT) as a function of VDD, in order to guarantee correct operation. These functions are illustrated in Figure 9., Figure 10., Figure 11. and Figure 12..

OSCin OSCout

CL1n

CL2

Figure 8. illustrates various possible oscillator configurations using an external crystal or ceramic resonator, an external clock input, an external resistor (RNET), or the lowest cost solution using only the LFAO. CL1 an CL2 should have a capacitance in the range 12 tST6_CLK1o 22 pF for an oscillator frequency in the 4-8 MHz range.

The internal MCU clock frequency (fINT) is divided by 12 to drive the Timer, the A/D converter and the Watchdog timer, and by 13 to drive the CPU core, as may be seen in Figure 11..

With an 8MHz oscillator frequency, the fastest machine cycle is therefore 1.625μs.

A machine cycle is the smallest unit of time needed to execute any operation (for instance, to increment the Program Counter). An instruction may require two, four, or five machine cycles for execution.

EXTERNAL CLOCK CRYSTAL/RESON ATOR option

ST6xxx

OSCin OSCout

NC

RC NETW ORK

RC NETW ORK option

ST6xxx

OSCin OSCout

3.1.1 Main Oscillator

The oscillator configuration may be specified by selecting the appropriate option. When the CRYSTAL/RESONATOR option is selected, it must be used witha quartz crystal, a ceramic resonator or an external signalprovided onthe OSCinpin. When the RC NETWORKoption is selected, the system clock is generated by an external resistor.

The main oscillator can be turned off (when the OSG ENABLED option is selected) by setting the OSCOFF bit of the ADC Control Register. The Low Frequency Auxiliary Oscillator is automatically started.

NC

RNET

INTEGRA TED CLOCK CRYSTAL/RESON ATOR option

OSG ENABLED option

ST6xxx

OSCin OSCout

NC

18/78

CLOCK SYSTEM (Cont'd)

Turning on the main oscillator is achieved by resetting the OSCOFF bit of the A/D Converter Control 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 fLFAO clock frequency.

3.1.2Low 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 fLFAO frequency. The A/D converter 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 until the Main Oscillator runs.

The Low Frequency Auxiliary Oscillator is automatically switched off as soon as the main oscillator starts.

ADCR

Address: 0D1h Ð			Read/Write
7							0
ADCR	ADCR	ADCR	ADCR	ADCR	OSC	ADCR	ADCR
7	6	5	4	3	OFF	1	0

Bit 7-3, 1-0= ADCR7-ADCR3, ADCR1-ADCR0:

ADC Control Register. These bits are not used.

Bit 2 = OSCOFF. 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 func-

ST62T52C ST62T62C/E62C

tions: 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 lines result in an effectively 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 (as illustrated in Figure 9.). In all cases, when the OSG is active, the maximum internal clock frequency, fINT, is limited to fOSG, which is supply voltage dependent. This relationship is illustrated in Figure 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 (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 fOSG: the maximum authorised frequency with OSG enabled.

Note. The OSG should be used wherever possible as it provides maximum safety. Care must be taken, however, as it can increase power consumption and reduce the maximum operating frequency to fOSG.

Warning: Care has to be taken when using the OSG, as the internal frequency is defined between a minimum and a maximum value 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).

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ST62T52C ST62T62C/E62C

CLOCK SYSTEM (Cont'd)

Figure 9. OSG Filtering Principle

(1)

(2)

(3)

(4)

(1)Maximum Frequency for the device to work correctly

(2)Actual Quartz Crystal Frequency at OSCin pin

(3)Noise from OSCin

(4)Resulting Internal Frequency

Figure 10. OSG Emergency Oscillator Principle

Main

Oscillator

Emergency

Oscillator

Internal

Frequency

VR001932

VR001933

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ST62T52C ST62T62C/E62C

CLOCK SYSTEM (Cont'd)

Figure 11. Clock Circuit Block Diagram

			POR
		: 13	Core
	OSG
			TIMER 1
MAIN	M	fINT	Watchdog
	U	: 12

OSCILLATOR

X

LFAO

: 1

Main Oscillator off

Figure 12. Maximum Operating Frequency (fMAX) versus Supply Voltage (VDD)

Maximum FREQUENCY (MHz)
8
7	NOT	4
6					3
	FUNCTIONALITYIS GUARANTEED THISIN AREA					fOSG Min (at 125°C)
						fOSG
5
4					2	fOSG Min (at 85°C)
3
2
					1
1	3
2.5		3.6	4	4.5	5	5.5	6

SUPPLY VOLTAGE (VDD)

VR01807J

Notes:

1.In this area, operation is guaranteed at the quartz crystal frequency.

2.When the OSG is disabled, operation in this area is guaranteed at the crystal frequency. When the OSG is enabled, operation in this area is guar-

anteed at a frequency of at least fOSG 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 fOSG.

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 fOSG.

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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-on Reset;

±by the digital Watchdog peripheral timing out.

±by Low Voltage 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 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 VDD has 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 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 an internal delay is initiated, in order 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

RESET

NMI MASK SET

INT LATCH CLEARED ( IF PRESENT )

SELECT

NMI MODE FLAGS

PUT FFEH

ON ADDRESS BUS

YES

IS RESET STILL

PRESENT?

NO

LOAD PC

FROM RESET LOCATIONS

FFE/FFF

FETCH INSTRUCTION

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 hysteresis effect. 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)

VDD

VUp

Vdn

RESET	RESET
	time

VR02106A

3.2.5 Application Notes

No external resistor is required between VDD and the Reset pin, thanks to the built-in pull-up device.

Direct external connection of the pin RESET to VDD must be avoided in order to ensure safe behaviour of the internal reset sources (AND.Wired structure).

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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 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 end of the initialisation routine, the MCU will continue by processing the instruction immediately following the RETI instruction. If, however, a pending interrupt is present, it will be serviced.

Figure 15. Reset and Interrupt Processing

RESET

JP	JP:2 BYTES/4 CYCLES

RESET

VECTOR

INITIALIZATION

ROUTINE	RETI: 1 BYTE/2 CYCLES
	RETI

VA00181

Figure 16. Reset Block Diagram

VDD			ST6
fOSC		CK	INTERNA L
			RESET
RPU		COUNTER
	AND. Wired
1)
RESD
RESET	RESET	RESET
POWER ON RESET
WATCHD OG RESET
LVD RESET
			VR02107A

1) Resistive ESD protection. Value not guaranteed.

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