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

From: Ethan Dicks <>
Date: Mon, 9 May 2016 22:34:29 -0400
Message-ID: <>
On Mon, May 9, 2016 at 1:51 PM, Kajtár Zsolt <> 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".


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Received on 2016-05-10 03:00:03

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