From: Marko Mäkelä (
Date: 2004-09-09 11:18:22

Hi Ruud,

> > Hmm, if you were copying individual files, wouldn't it be 
> > possible to tell the CBM-HD to LISTEN and the 8250 to TALK?
> You mean sending a TALK to the 8250 and a LISTEN to CBM-HD? On itself a good
> idea as there is only one transfer par byte instead of two as it is now.
> Transferring files isn't a problem as the sender will activate EOI at the
> end of the file. But how are you going to tell the sender to activate EOI at
> the 256th byte?

I didn't think that it would be a solution for disk transfers; I just mentioned
it as a compatibility test case for your CBM-HD.

Come to think of it, it might work also for disk image transfers.  You'd write
a program for the 8050 or 8250 and start it with M-E.  The program would wait
for the LISTEN or TALK request, and then it would start transfering disk
sector data.  The CBM-HD would receive all data in a single file.  Copying
back to disk wouldn't work as easily.

> But the docs state that one can only read from 1 up to 255 bytes. I need to
> read 256. I could try if 0 is translated as 256 otherwise I have to do it in
> two batches.

cbmlink uses M-R length 0 and copies 256 bytes at a time.  I don't remember
if 0 means "infinite"; you will have to test it.

> More worrying is the fact that I only can write up to 34 byte. Is the
> computer to blame or the drive?

The drive.  It has a fixed-size command buffer.  It'll input the data to the
buffer, and then copy it to the desired location.  M-R reads directly from
the specified address.

What language is CBM-HD written in?  Are you planning to release the source
code?  I'd be interested in a GNU/Linux port.  I have an old IEEE-488 ISA card
lying around.  I hope that the code is modular enough to support different
types of IEEE-488 interfaces.


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