Re: Calling all DOS-heads

From: Nate Lawson <>
Date: Fri, 30 Mar 2012 08:12:20 -0700
Message-Id: <>
On Mar 30, 2012, at 5:29 AM, Ingo Korb wrote:

> Jim Brain <> writes:
>> load"$",9
> A bit small, but workable unless you need to decipher the timing marks.
> 180x100? Did you accidentally upload/link a thumbnail of the image you
> wanted to show?

He uploaded another copy of this one that is readable.

>>   * ATN_IN cycles a few times (zoomFLoppy), trying to get a response.
> I don't see that in the screenshot? Besides, why would it have any
> reason to wiggle ATN? It can tell that there is at least one drive on
> the bus because DATA_bus went low within 1ms of ATN_bus low and there is
> no timeout for any further response from the drive at that point because
> it may currently work on a very long command (e.g. N or V).

In the without_ack case, the DATA line never goes low so the ZF tries a few more times of toggling ATN before giving up and reporting "device not present".

>> I don't understand why the DOS never notices ATN at 9.443ms
> It's busy reading data from the disk to create the directory listing the
> host just asked for.

That's an interesting idea.

I did send Jim a special firmware that will wait forever for DATA to be acked. But perhaps it's never ACKed in this case since the ROM code expects the circuit to handle it?


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Received on 2012-03-30 16:00:10

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