25/5/'98



Re single steps

It would seem that the PIC tests the state of the interrupts during one of
the first phases of the internal clock, and thus does not perfrom the next
instruction before going back into the interrupt routine.

Thus now comes the problem "How to do it". It has been suggested that a
counter be placed on the OSC line, yuck! I have decided that I will use the
internal timer to schedule an interrupt, 8 clock cycles after the last
instruction in the routine. An external pin will be used to indicate a
single step (debounced with a F/F). To activate the S/S the code will enable
the timer interrupt and a NOP will be placed after the enable instruction,
thus from that point on I will be able to see I/O use, great for debugging!

I will let you all know how it goes!

Dennis