ST6280BQ1 STMICROELECTRONICS [STMicroelectronics], ST6280BQ1 Datasheet - Page 23

• Manufacturer Part Number: ST6280BQ1
• Description: 8-BIT OTP/EPROM MCU WITH LCD DRIVER EEPROM AND A/D CONVERTER
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

3.3 DIGITAL WATCHDOG
The digital Watchdog consists of a reloadable
downcounter timer which can be used to provide
controlled recovery from software upsets.
The Watchdog circuit generates a Reset when the
downcounter reaches zero. User software can
prevent this reset by reloading the counter, and
should therefore be written so that the counter is
regularly reloaded while the user program runs
correctly. In the event of a software mishap (usual-
ly caused by externally generated interference),
the user program will no longer behave in its usual
fashion and the timer register will thus not be re-
loaded periodically. Consequently the timer will
decrement down to 00h and reset the MCU. In or-
der to maximise the effectiveness of the Watchdog
function, user software must be written with this
concept in mind.
Table 8. Recommended Option Choices
Functions Required
Stop Mode
Watchdog
Watchdog behaviour is governed by one option,
known as “WATCHDOG ACTIVATION” (i.e.
HARDWARE or SOFTWARE) (See
In the SOFTWARE option, the Watchdog is disa-
bled until bit C of the DWDR register has been set.
When the Watchdog is disabled, low power Stop
mode is available. Once activated, the Watchdog
cannot be disabled, except by resetting the MCU.
In the HARDWARE option, the Watchdog is per-
manently enabled. Since the oscillator will run con-
tinuously, low power mode is not available. The
STOP instruction is interpreted as a WAIT instruc-
tion, and the Watchdog continues to countdown.
When the MCU exits STOP mode (i.e. when an in-
terrupt is generated), the Watchdog resumes its
activity.
“HARDWARE WATCHDOG”
“SOFTWARE WATCHDOG”
Recommended Options
ST62T80B/E80B
Table
8).
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