From: Baltissen, GJPAA (Ruud) (ruud.baltissen_at_abp.nl)
Date: 2004-07-05 16:23:19

Hallo allemaal,

For the ???th year in a row I'm still working on my, let's say, 64HDD
version for the PET/CBM. In general things work fine. But a big
troubleshooter was, and still is, the handling of the DIRECTORY command. 

For those who forgot: this is the BASIC V4 version of 'LOAD "$",8' with two
major differences:
- the output from the drive is sent to screen, not saved as a BASIC file
- the transfer is interrupted everey one or two bytes by te CBM for one or
another reason

Most of the transfer is not time critical. The only time critical is that
you HAVE to start sending data within ??? uSecs after receiving TALK
otherwise the computer responds with "FILE NOT FOUND". This time critical
thing also applies to the time between bytes. 
The actual transfer of the bytes is done using handshaking, not time
sensitive clocking as with the IEC-protocol.
The stupid thing is that, just because of time sensitivity described above,
everything I have to sent is placed in RAM so during a transfer IMHO most of
the time the program is waiting for the handshake signals and checking ATN
in between. And yet sometimes the CBM responds with a "DEVICE NOT PRESEN?"
which means the PC hasn't noticed a ATN for some reason. 

The only thing I can think of is that a PC-interrupt consumes to much
precious time. So I'm thinking of shutting down some interrupts in one or
another way. Who has experience (I'm especially thinking of Nick and Andre)
and can give me some usefull tips ?
Many thanks IA !!!

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



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