Re: Mysterious 1541 behaviour

From: silverdr_at_wfmh.org.pl
Date: Mon, 21 Jan 2013 12:42:57 +0100
Message-Id: <2EE95516-6B7F-4201-9A8E-1EDACB0BC3B2@wfmh.org.pl>
On 2013-01-21, at 02:43, Pete Rittwage wrote:

> Generally this looks like transfer/copy code from BurstNibbler.

I believe that it is more or less generic approach used by many programs. AFAIR burstnibbler and others used ATN line for handshaking, which I very much prefer to avoid using.

> The idea
> is if there is a delay in receiving the byte-ready signal, the hardware is
> probably waiting for a sync signal to end, so it sends a "sync" data byte
> back to the C64 (or drive RAM is extra RAM is used) every so often.  This
> makes it easier to "write" this area back to the disk as a sync.  The
> delays are cycle-counting to guess the actual sync length. This is also
> density specific, so these delays are usually runtime-modified.

Hm - Not sure if I understand but I don't even spin the motor. I have no disk in drive. I turn off IRQs. And the only thing I want to achieve is a reliable (handshaken) data transfer, regardless of the timing. Just transfer between CPUs. Right now it seems to be randomly corrupting the data like if there were still some other factors affecting the states of the serial lines. And since I already started to disassemble my DD3 board, I currently don't even have the real hardware to verify this on and check whether it is not only VICE's "feature".

-- 
SD!
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Received on 2013-01-21 12:00:04

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