🚀 go-pugleaf

I just got my 68000 development kit for the mac last week.  I am
interested in writing my own MIDI interfaces so that I can control
my MIDI synth (DX7).  In the copy of "Inside Macintosh" that comes
with the development kit, the serial drivers are discussed.  However,
in the Serial Driver's Manual, there is no mention of how to get
nonstandard baud rates - they just give the typical ones.  I'm sure
the number you use for a particular baud rate is simply counted down
to get you the baud rate, but it does not seem that simple.  One problem
is that the baud rate number to use for the function SerReset is only
9 bits, the Z8530 uses a 16 bit register for the baud rate.  Probably,
the nine bits are mapped to the least 16 bits, with the rest filled in
with zeros.  If this were the case, then you would expect that

	baud rate = sampling frequency / number to load   or

	baud rate = sampling frequency / (number to load + 1)

but this does not seem to be the case.  Maybe they are playing around
with the X2, X4, etc clocks for the Z8530.

Anyways, does anyone have any light to shed on the subject?  To put it
all in a nutshell - how do you reset the Z8530 to get a 31.25 k baud?

Thanks,    Steve O'Connell   ihnp4!harpo!sso