ST6285BQ1 View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST6285BQ1

8-BIT OTP/EPROM MCU WITH LCD DRIVER, EEPROM AND A/D CONVERTER

STMicroelectronics 

ST62T85B/E85B

3.3 DIGITAL WATCHDOG

The digital Watchdog consists of a reloadable

downcounter timer which can be used to provide

controlled recovery from software upsets.

Watchdog behaviour is governed by one option,

known as “WATCHDOG ACTIVATION” (i.e.

HARDWARE or SOFTWARE) (See Table 8).

The Watchdog circuit generates a Reset when the In the SOFTWARE option, the Watchdog is disa-

downcounter reaches zero. User software can bled until bit C of the DWDR register has been set.

prevent this reset by reloading the counter, and When the Watchdog is disabled, low power Stop

should therefore be written so that the counter is mode is available. Once activated, the Watchdog

regularly reloaded while the user program runs cannot be disabled, except by resetting the MCU.

correctly. In the event of a software mishap (usual- In the HARDWARE option, the Watchdog is per-

ly caused by externally generated interference), manently enabled. Since the oscillator will run con-

the user program will no longer behave in its usual tinuously, low power mode is not available. The

fashion and the timer register will thus not be re- STOP instruction is interpreted as a WAIT instruc-

loaded periodically. Consequently the timer will tion, and the Watchdog continues to countdown.

decrement down to 00h and reset the MCU. In or-

der to maximise the effectiveness of the Watchdog When the MCU exits STOP mode (i.e. when an in-

function, user software must be written with this terrupt is generated), the Watchdog resumes its

concept in mind.

ct(s) Table 8. Recommended Option Choices

u Functions Required

rod Stop Mode

Obsolete Product(s) - Obsolete P Watchdog

activity.

Recommended Options

“SOFTWARE WATCHDOG”

“HARDWARE WATCHDOG”

23/78

23

Share Link: