Date   : Mon, 24 Sep 2001 19:33:09 +0100
From   : "Richard Gellman" <r.gellman@...>
Subject: Re: Disc fault 04 and ADFS Checksums

>Why not disassemble the DFS and find the error message routines, so you can
>determine why?

Emulating it is one thing, I couldn't disassemble the DFS looking for that
stuff :)

>How did you do that? I'm sure all DDOS needs is different addresses and a
>slightly different control register format

If my emulation was complete, yes. But in the process of adding DDOS
support, I need to add extra bits to the existing code. As it turns out (For
information purposes) Disc Fault 04 is "Data Lost" and means that the bbc
either didn't read the data in quick enough, or didn't write it out quick
enough. I found out this was due to Status bit 2 being set meaning "Not
Track 0" for type 1 commands, but not being reset for type 2 (read/write)
commands, whereby bit 2 being set indicates data lost. So I fixed that one,
and got it working perfectly :)

My next question, is how the hell do you calculate an ADFS FS Map sector
checksum? I'm adding ADFS to the new disc options, but my "new discs" have
bad fs maps on them because of an incorrect checksum byte on each sector.

-- Richard Gellman

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