Problem with ST7LITE05 Watchdog Timer

[clanuchnik]

Posted on October 23, 2003 at 12:09

Problem with ST7LITE05 Watchdog Timer

[clanuchnik]

Posted on October 20, 2003 at 12:11

1) I configured the MCU for hardware WDT and no reset on Halt

2) Before executing the Halt instruction I wrote this code:

bset LTCSR,#0; Clear Watchdog Timer

halt

3) After reset vector fetch I wrote this code:

.main bset LTCSR,#0; Clear Watchdog Timer

4) When the MCU is stucked and the WDT resets it I can see in the scope in the external reset pin(3) the reset pulse of about 30 us and then it is released for about 45 us. I suppose it belongs to the internal reset 256 Tcpu + the Vector fetch time and then the low reset pulse again.

5) The MCU fails to wake up in normal mode because the WDT is not fully cleared and I don't know what else I have to do in order to assure the WDT won't reset the MCU immediately after RESET sequence.

bset LTCSR,#0; Clear Watchdog Timer

seems not to be enough for this purpose even before entering Halt mode and after Reset vector fetch

Thanks

Claudio

[anshul]

Posted on October 22, 2003 at 14:59

Did you clear the WDGRF Flag after the Watchdog Reset.

If you have not cleared it, this could be the reason why the microcontroller is immediately reset again.

I hope this helps.

[jatin]

Posted on October 23, 2003 at 12:09

The only thing required is to refresh the watchdog counter before entering into the halt mode; So make sure it is done