Re: C64 Expansion Port IO1 and IO2 and PEEK and POKE

Fascinating, thank you all for the explanations!
On May 9, 2016 11:06 PM, "Julian Perry" <jp@digitaltapestries.com> wrote:

> Hello Ethan,
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> Tuesday, May 10, 2016, 12:34:29 PM, you wrote:
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> *> On Mon, May 9, 2016 at 1:51 PM, Kajtár Zsolt <*soci@c64.rulez.org
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> *> wrote: >>> ...leave monitor, do poke 57088,123 and enter the monitor
> again, you see this: >> Apart from the wrong cycle numbers it's just the
> regular dummy read for fixing >> up the high part of address after
> indexing. It's expected as it's not optional >> for a write. > This rings a
> bell from my days of programming the Apple II... The I/O > there, unlike
> CBM equipment, can be triggered by simply reading a > specific address
> (writing specific values not required, unlike, say, > fiddling VIA or CIA
> register contents).  We had to be careful about > reads vs writes because
> of that "double tap". > -ethan * <jp@digitaltapestries.com>
> That can happen with the CIA/VIA timers too, and was a common trick
> (apparently) to clear both latches at the same time onthe Atari 2600's 6532
> RIOT.
>
> Julian
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