ST7260E1 STMicroelectronics, ST7260E1 Datasheet - Page 44

• Manufacturer Part Number: ST7260E1
• Description: LOW SPEED USB 8-BIT MCU FAMILY WITH UP TO 8K FLASH/ROM AND SERIAL COMMUNICATION INTERFACE (SCI)
• Manufacturer: STMicroelectronics

Specifications of ST7260E1

• 4 Or 8 Kbytes Program Memory: high density Flash (HDFlash), or FastROM with readout and write protection

Watchdog timer (WDG)
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Watchdog timer (WDG)
Introduction
The Watchdog timer is used to detect the occurrence of a software fault, usually generated
by external interference or by unforeseen logical conditions, which causes the application
program to abandon its normal sequence. The Watchdog circuit generates an MCU reset on
expiry of a programmed time period, unless the program refreshes the counter’s contents
before the T6 bit becomes cleared.
Main features
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Functional description
The counter value stored in the CR register (bits T6:T0), is decremented every 49,152
machine cycles, and the length of the timeout period can be programmed by the user in 64
increments.
If the watchdog is activated (the WDGA bit is set) and when the 7-bit timer (bits T6:T0) rolls
over from 40h to 3Fh (T6 becomes cleared), it initiates a reset cycle pulling low the reset pin
for a period of t
The application program must write in the CR register at regular intervals during normal
operation to prevent an MCU reset. This downcounter is free-running: it counts down even if
the watchdog is disabled. The value to be stored in the CR register must be between FFh
and C0h (see
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Programmable free-running counter (64 increments of 49,152 CPU cycles)
Programmable reset
Reset (if watchdog activated) when the T6 bit reaches zero
Optional reset on HALT instruction (configurable by option byte)
Hardware Watchdog selectable by option byte.
The WDGA bit is set (watchdog enabled)
The T6 bit is set to prevent generating an immediate reset
The T5:T0 bits contain the number of increments which represents the time delay
before the watchdog produces a reset.
Table 23: Watchdog timing (f
DOG
(see
Table 62: Control timings on page
CPU
= 8 MHz) on page
114).
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ST7260xx