Visible to Intel only — GUID: iga1401398647746
Ixiasoft
Visible to Intel only — GUID: iga1401398647746
Ixiasoft
23.3.4. Configuring the Timer as a Watchdog Timer
- Set the Timeout Period to the desired "watchdog" period.
- Turn off Writeable period.
- Turn off Readable snapshot.
- Turn off Start/Stop control bits.
- Turn off Timeout pulse.
- Turn on System reset on timeout (watchdog).
A watchdog timer wakes up (comes out of reset) stopped. A processor later starts the timer by writing a 1 to the control register's START bit. Once started, the timer can never be stopped. If the internal counter ever reaches zero, the watchdog timer resets the system by generating a pulse on its resetrequest output. The resetrequest pulse will last for two cycles before the incoming reset signal deasserts the pulse. To prevent an indefinite resetrequest pulse, you are required to connect the resetrequest signal back to the reset input of the timer.
To prevent the system from resetting, the processor must periodically reset the timer's count-down value by writing one of the period registers (the written value is ignored). If the processor fails to access the timer because, for example, software stopped executing normally, the watchdog timer resets the system and returns the system to a defined state.