Wed, Oct 05, 2022 at 05:41:15PM +0100, smf wrote: >NMI is edge triggered, IRQ is level triggered. > >If IRQ stays low then it will fire again when you RTI out of the >interrupt handler. > >NMI has no mask, so it only fires when it transitions from high to low & >there is nothing to stop another NMI from being triggered while the >handler is still running. My point was that another high-to-low transition cannot occur as long as something is holding the line low. The trick to "disable NMI" (including the Restore key) on the Commodores is to program a PIA, VIA, or CIA to pull the line low and let it remain there. This would obviously require a custom NMI handler to be installed, at the minimum, consisting of the RTI instruction. MarkoReceived on 2022-10-05 19:05:03
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