Re: VIC-20 "Pause" button

From: Michał Pleban <*lists_at_michau.name*> Date: Sat, 13 Jul 2013 16:18:58 +0200 Message-ID: <51E161D2.8090801@michau.name> · lists_at_michau.name

Hello!

Peter Rittwage wrote:

> There is also a C64 "slowdown" cart which attached the IRQ line to a
> timer and potentiometer. It would inject IRQ's to slow down, or pause,
> the running program.
> It was a simple cart circuit, and it had really odd effects on different
> games.

That's a refreshingly simple idea, but injecting random IRQs can really
confuse running software (besides the fact that it can have interrupts
disabled).

How about:

* Using the DMA line to halt the CPU completely (is that even possible)?

* Using the NMI line with ROM control lines to throw the computer into
the UltiMax mode and place a loop at the NMI handler? Quite more
complex, but one 16V8 would do.

Regards,
Michau.

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