Re: 8250 help needed

From: Andre Fachat (
Date: 1999-06-04 15:47:20

Nicolas Welte wrote:
> Hi,
> does anybody know how to do the following things on a 8250:
> Disable head bump on error and/or set the number of retries on an error.

The problem is that the DOS reads the number of sides from values given
by the FDC during the reset routine negotiation, and fills up some
tables - the very same DOS 2.7 ROM can be used on 4040/8050/8250/1001
disk drives, only the FDC controller ROM is different and tells 
the IP CPU which type of drive it is.

Have to look at the ROM code.

> This is a single m-w command on the 1541. I need it to read in some disk
> images with prlink, and every time I read a 8050 format disk, there is
> an 21 read error on track 78, naturally. The drives answers with the

You could do an intermediate copy from the 8050 to a disk image
on an 8250 disk (with the disk2file, modified to stop at track 77), 
and transfer this disk.

> Format an 8050 format disk (single sided). I guess this can also be done
> with a single m-w command. But which one?

If you manage to initialize the 8250 as 8050, this should be no problem.
But if you don't, the format code is a mess...
(The IP processor copies code to the common buffers and lets the 
FDC processor execute it...

looking at the reset code at F2B7 should reveal what you need.
Ok, it writes the code from c370 into the FDC buffer and executes it.
This code checks the hardware and e.g. sets the number of sides to 
$04ac in the FDC address range, should be $10ac for the IP processor.

If you're lucky that's just that. But in the routine from C412 
around c4c4 some other tables are filled depending on the number
of sides...

If you know how to do it, tell us :-)


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Andre Fachat, Institute of physics, Technische Universitšt Chemnitz, FRG
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