From: Ruud Baltissen (g.baltissen_at_hccnet.nl)
Date: 2002-01-19 23:01:44 

Hallo Michael and others,

>    Delay(1000);
>    AtnLo;
>    ByteOut($28, False);
>    ByteOut($E0, False);
>    AtnHi;

I appended this sequence but no result. So I tried the Initialise and 
Validate command, no results either. Studying the read byte stream of 
the Initialise command between my 8032-SK and 8250 I noticed $3F (= 
Unlisten) as last command. Appended this to "read directory" sequence 
and ... it worked: LED went off.

Next problem was the not working "I" and "V". So I started stepping 
through the program and suprise... both commands now worked. It 
appeared that when sending all bytes in a row, nothing happened. A 
delay before the close command did the trick. 
In BASIC you can give the command: OPEN4,8,15,"V":CLOSE4

This results in the drive performing the demanded task but as you can 
see there is no delay. My first thought was that BASIC is so slow that no 
delay was needed. Writing this sentence another thought struck me: the 
READY prompt does not appear immediatly, HOW DOES THE 8032 
KNOW THAT THE COMMAND ISN'T FINISHED YET?
So I hacked my program that copies the datastream between the 8032 
and 8250 and found out that the line NRFD (Not Ready For Data) was 
held (L), most likely by the drive as the 8032 has no reason to do so.

So I know know where to look for :) But one question remains: the 1541 
has no NRFD-line, how is the feedback done here (maybe pulling DATA 
or CLK or even both Low)?

   ___
  / __|__
 / /  |_/     Groetjes, Ruud
 \ \__|_\
  \___|       http://Ruud.C64.org


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