On 14/06/2018 23:27, Nejat Dilek wrote: > I already know it but I'm not talking about software. I'm talking > about hardware and my comments were to the statement "which would hold > the NMI line down, preventing NMI from working". I shared my doubt as > to the "line being held low" or "hardware generating nmi just waiting > for an ACK and not generating any more nmi interrupts.". I think the > latter is correct. > > Since NMI to be generated by this special hardware, running software > on the c64 can't prevent it happening. Marko Makela's finding is only > relevant for the stock hardware. The CPU NMI is connected to the CIA output and the restore key. The CIA output is left low because it is not acknowledged. When you hit the restore key and it also sets the line low, there is no NMI because the line hasn't gone from high to low. The CIA has no knowledge that the restore key can also generate NMI's. For your theory to be correct the NMI has gone high and somehow the CIA is telling the restore key that because it's timer hasn't been acknowledged then the restore key should not interrupt.Received on 2018-06-15 01:01:25
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