Re: 6526A synchronous serial behavior?

From: Wolfgang Moser <womo_at_news.trikaliotis.net>
Date: Thu, 22 Sep 2011 21:57:56 +0200
Message-ID: <j5g3od$ijo$1@vs5413.trikaliotis.net>
Hi Nate,

Nate Lawson schrieb:
> On Sep 21, 2011, at 3:22 PM, Segher Boessenkool wrote:
> 
> It's 500 Kbit/sec inbound to the 1571. Some devices receive it just
> fine, others don't. I'm going to try reducing the clock rate slowly
> and see where it becomes reliable. If it truly is synchronous with

if it is different behavior from drive to drive then this let's me think
on different CIA revisions. 6526 vs. 6526A vs. 8520, you know even VICE
does support two different 6526 types, the "old" and the "new" one which
have some off-by-one clock cycle differences. I don't know about the
exact details, but since the shift registers may be the worst
studied/tested functional blocks of the CIA, this could be a reason.

Maybe you want to have a look for a piece of CIA type detection code and
check, if there is a relation beweeten "unreliable" 1571 drives and a
certain CIA type.


Womo

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Received on 2011-09-22 21:00:03

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