Re: Mysterious 1541 behaviour

From: Pete Rittwage <>
Date: Mon, 21 Jan 2013 08:24:09 -0500 (EST)
Message-ID: <>
On Mon, January 21, 2013 6:42 am, wrote:
> 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".

So this is existing code from something or is it something you are
developing?  I may have misunderstood- I thought you were asking about an
existing technique you found somewhere....


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Received on 2013-01-21 14:00:03

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