Re: Fast serial interrogation timing question

On 8/20/2013 5:09 PM, Ingo Korb wrote:
> Jim Brain <brain@jbrain.com> writes:
>
>> Does anyone have any thoughts on why the "can you do fast serial"
>> interrogation happens even before ATN falls on the C128/C128D/DCR?
> The part that happens before ATN isn't an interrogation, it's just an
> announcement that the computer is fast serial-capable. The drive is
> still addressed using slow serial for all ATN "command bytes" and when
> it determines that it is addressed and should act as a listener, it
> responds with a single fast serial byte to signal to the computer that
> it can use fast serial. If the drive is addressed as a talker, it just
> sends data via fast instead of slow serial.
>
> -ik
My terminology might be incorrect, but my question remains the same.  
Why send the byte before ATN goes low?  It's non data information (maybe 
not a command, but it is capability information, not data), so it should 
be sent while ATN is low.

Jim


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