Mike Palmer

STOP instruction with IRQ low? - MC68HC9S08GB32

Discussion created by Mike Palmer on Jul 17, 2008
Latest reply on Jul 19, 2008 by bigmac

What happens when a 9S08GB32 executes a STOP intruction when the IRQ pin is low?

We use stop1 in our product for the very, very low power consumption it offers and use IRQ to wake it up. Normally everything is fine but we have found that if conditions are "just so" and our shutdown logic executes, the code may inadvertently run the stop instruction when IRQ is still low. It appears to me that the micro doesn't actually stop and re-start as if a POR occured but may continue executing at the instruction following the stop opcode.

This makes bad things happen in our code... We're working to correct the code to prevent this but I'm wondering if someone has any information on what the uC actually does when IRQ is already low and stop executes.



Added p/n to subject.

Message Edited by NLFSJ on 2008-07-17 07:28 AM