Re: Calling all DOS-heads

From: Jim Brain <>
Date: Fri, 30 Mar 2012 12:24:38 -0500
Message-ID: <>
On 3/30/2012 12:21 PM, Nate Lawson wrote:
> I wonder if something is clearing the flags byte?
> In the ROM, an interrupt caused by ATN leads to the code at $E853 storing a flag for the main loop. The main loop comes around and finds the flag active and calls $E85B in the normal case. We see this working for the first part (open command).
> It then releases the CLK line at $E86D and then sets the DATA line low at $E870. It then sets ATNA and then waits for either ATN to be released (entire command done) or CLK to be released (first command byte ready). If CLK was released, it begins reading the command byte.
> So maybe the return from handling the directory routine or close routine behaves differently? I wonder if something is getting reinitialized.
I'll try another test.

I put ATN_ACK on a switch.  Running with code that waits indefinitely, 
I'll turn it off initially, do the $, and wait 10 seconds or so, then 
turn it on and see if everything works.

My guess is that DATA is not brought low, but that the code is waiting 
on bytes to be sent.


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Received on 2012-03-30 18:00:20

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