Watchdog Timer of ADUC842

I have Serial ISR which needs to be executed whenever there is handshaking between my module and host.

For that only i have enabled all the interrupts in my main function...
i am supposed to set watchdog timer too...
watchdog timer will help the controller to come out of errorneous condition.

for setting watchdog timer,i should disable all the interrupts ,set the watchdog timer and then enable all the interrupts.

I cant do this...hope you have understood my problem...

regards
mayuri

I have Serial ISR which needs to be executed whenever there is handshaking between my module and host.

For that only i have enabled all the interrupts in my main function...
i am supposed to set watchdog timer too...
watchdog timer will help the controller to come out of errorneous condition.

for setting watchdog timer,i should disable all the interrupts ,set the watchdog timer and then enable all the interrupts.

I cant do this...hope you have understood my problem...

regards
mayuri

No. We have not understood your problem, for the simple reason that we don't see a problem.

1) You can enable the watchdog timer before you enable the other interrupts.
2) You can disable interrupts while playing with the watchdog - and there are multiple ways to do that.

So exactly what is your problem?

CLR EA //disable interrupts while writing

SETB WDWR //allow write to WDCON

MOV WDCON,#72H //enable WDT for 2.0s timeout

SETB EA //enable interrupts again (if rqd)

this is what i am supposed to write in my main function if i am using watchdog.

but if i clear my interrupts,den my ISRs wont be executed.

i need to keep my interrupts on always

CLR EA         //disable interrupts while writing
SETB WDWR      //allow write to WDCON
MOV WDCON,#72H //enable WDT for 2.0s timeout
SETB EA        //enable interrupts again (if rqd)

How long, exactly, do you think that code sequence takes to execute?

You only need to do it once- at startup.

Do you really think that it will make any significant difference if you do this immediately before you enable your other interrupts??

"if i clear my interrupts,den my ISRs wont be executed"

Until you enable them again!!

"i need to keep my interrupts on always"

See above - you only need to do this once, and only at the very start of your code - where is the problem in that?!

ok got it...
thnx a lot...

Note that there is a big difference between disabling and clearing interrupts.

Disabling interrupts means devices with interrupt support will detect events and latch the interrupt state. But the device isn't allowed to kick the processor core to switch to the ISR. When the interrupts are enabled again, any pending interrupts will be serviced.

Clearing interrupts is telling peripherials that any pending interrupts should be permanently forgotten. A completely different thing.

Your play with CLR EA is disabling interrupts. It is not clearing any interrupts. So any interrupts detected before or during this critical section will trig after you enable interrupts again.

Thnx for the info

regards,
Mayuri