Re: u1 command 2040 disk drive

From: Mike Naberezny <mike_at_naberezny.com>
Date: Thu, 22 Apr 2021 10:14:27 -0700
Message-ID: <b5a0bcb4-962f-4bcd-4aab-c342563faea6_at_naberezny.com>
On 4/22/21 2:36 AM, smf wrote:
> I tried to use a 2040 in vice (c64+ieee), does anyone know if the U1
> command is supposed to work or is it a known bug in the 1.2 rom?
> 
> The first byte of every sector is always returned as 137 ($89), but the
> rest of the sector is fine.

When I disassembled the BIOS for the SoftBox, I found some interesting code 
that may be related:

https://github.com/mnaberez/softbox/blob/4a5702cd14a16eab2a9c6a27923a912e5371e9cf/bios/1983-06-09.asm#L2222-L2287

> Work rounds or fixes welcome....

After issuing U1, the SoftBox uses M-R to read the first byte.  It then uses 
B-P to read the remaining bytes.

Regards,
Mike

-- 
Mike Naberezny (mike_at_naberezny.com) http://6502.org
Received on 2021-04-22 20:00:03

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