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HS12 Interrupts with CALL

Question asked by Gilbert Gagne on May 11, 2010
Latest reply on May 13, 2010 by Gilbert Gagne

My application uses the Modulus downcounter to generate interrupts when the count reaches zero to update a real time clock. Calling a subroutine in ppage $22 hangs up the micro unless Modulus interrupts are disabled. The interrupt service routine is in a non-paged location.  The same thing happens with serial communications to a LCD display. I've had to change serial operations to a polling mode to avoid those interrupts.


Why can't interrupts be used with the CALL function? The RTI instruction does not seem to restore the ppage value and this may be the reason. Can anyone shed some light on this problem?


The processor is a MC9S12DP512.