I assume only two priorities are available. Let the 10 ms interrupt can be at high priority and remaining others are at low priority.

Now 10 ms external interrupt is executed and inside the ISR save the current IP, and redefine the IP to have high priority for 5 ms (Timer) interrupt and others at low priority.

And initiate the 5ms timer now. So after elapse of 5 ms from external interrupt, the 5 ms will execute and return to 10 ms interrupt, if not completed.

Once 10 ms is over, ohter low priority can execute.


V.Nagarajan