Is there a way to poll for an interrupt on the ‘816? The software needs to poll for an interrupt (running with interrupts masked off) and execute an interrupt routine if there’s an interrupt present, otherwise continue on with the program. I don’t think the wai instruction can be used for this because it’ll wait for an interrupt. The software doesn’t need to wait. The best I could come up with was the following code:

It turns the poll into a subroutine call. Seems like a lot of overhead.

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Doesn't
PHP
CLI
PLP
do the trick?

Hey thanks, that'll work. Wrapped up in a macro that's ideal.

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Even CLI : SEI should do, and takes only 4 cycles in the no-interrupt case. If I was not already set, then any interrupt would be taken immediately and you wouldn't need to poll for it. The interrupt itself will save and restore P around the ISR.

Yup that works too. (I found that one myself after the large hint).
I have it wrapped up in a macro called 'pfi'. Since the system is running with interrupts disabled there's no need to push / pull the status reg.
All the interrupts are still connected to a port so all that's needed in the IRQ routine is to read the port to see who interrupted.
Hopefully I can get a little co-operative multi-tasker going.

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