General question re: interrupts

[Meterman58761]

If the only interrupt I'm working with is driven by the NMI pin on the CPU, are any SEI / CLI instructions therefore meaningless?

Or are there internal IRQs within the processor that are not otherwise addressed by the user's code?

[BigEd]

Indeed, SEI/CLI only makes a difference for IRQs, so no need for those, and if you have them they won't have any effect.

[Meterman58761]

Thank you! It just amazes me the code I've been looking at even works with all the cruft and inefficient coding I've dug out so far.

[BigDumbDinosaur]

I suggest you read Garth's interrupt primer so you will become real familiar with how the 6502 reacts to interrupts.

[AndrewP]

BigDumbDinosaur wrote:

I suggest you read Garth's interrupt primer so you will become real familiar with how the 6502 reacts to interrupts.

Yup, I can second that; I've got it printed out behind me. I found it incredibly useful. That and your Investigating 65816 interrupts too (if using 65816).

[BigDumbDinosaur]

AndrewP wrote:

Yup, I can second that; I've got it printed out behind me. I found it incredibly useful. That and your Investigating 65816 interrupts too (if using 65816).

The 65C816 interrupts article does repeat a few items in Garth's piece, but was focused on the 65C816's more powerful interrupt capabilities.

Incidentally, the 816 article posted here is out-of-date. The most up-to-date version is on my POC website.