Re: Fast Serial Detection (was Re: Disk drive timing)

From: MagerValp (MagerValp_at_Goth.Org)
Date: 1998-08-24 19:38:06

>>>>> "MagerValp" == MagerValp  <MagerValp@Goth.Org> writes:

Ojala> Anyway, a somewhat different but related question I'm trying to
Ojala> get an answer to is: How does the C128 ROM detect if the drive
Ojala> is Burst-capable?

MagerValp> It's in my C128 PRG, which is at home, but I think the C128
MagerValp> it jiggles the extra line (/SRQ?) and waits for something
MagerValp> to answer.

At home now, with the PRG in my lap. The first paragraph of the Fast
Serial Bus section reads:


To function as a fast talker, the system must be addressing a fast
device, such as the 1571 disk drive. When addressing any device, the
C128 sends a fast byte, toggling the SRQ line eight times, with the
ATN line low. If the device is a fast device, it will record the fact
that a fast controller accessed it and respond with a fast
acknowledge. If the device is a slow device, no response is delivered
and the C128 then assumes it is talking with a slow device. The status
of drive speed is retained until the device is requested to untalk or
unlisten, if an error occurs, or if a system reset occurs.

    ___          .     .  .         .       . +  .         .      o   
  _|___|_   +   .  +     .     +         .   .     +    + Per Olofsson
    o-o    .      .     .   o         +             MagerValp@Goth.Org
     -       +            +    .
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