Re: Reproducing the 6522 shift register bug

From: smf <smf_at_null.net>
Date: Tue, 2 Jan 2024 12:21:05 +0000
Message-ID: <7b4b0d34-811f-4b3a-9ee9-50ce957fa638_at_null.net>
If you want to know whether you're experiencing the "shift in under
control of external input pulses" bug (there are other bugs in the 6522)
then you work round the bug by creating an adapter using the schematic here:

http://forum.6502.org/viewtopic.php?f=4&t=2175

If the code works fine with the adapter and breaks without, then you
know you have found the issue.

You will also be one step closer to implementing fast serial support on
the VIC-20.

On 23/12/2023 23:00, Dave McMurtrie wrote:
> The good news is that the data that is output by the receiver isn't always correct. So either I am successfully demonstrating the 6522 shift register bug or I'm just misunderstanding how to use the 6522 properly and my code is wrong.
Received on 2024-01-02 14:00:03

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