4 Aug
1997
4 Aug
'97
8:01 a.m.
There is what appears to be an RC clock composed of a
4.7 nF capacitor and
a multi-turn trimmer potentiometer in the upper left corner of the M7260
data path board in my 11/10. It looks like this clock feeds a 74197
counter, which has a 5-position rotary switch connected (presumably for
selecting what the incoming clock is divided by). I'll put a scope on pin
40 of the UART after I power the machine up to see what effect the rotary
switch has on the UART clock. It seems likely that the rotary switch is
used for making large changes in the baud rate and the trimmer is used for
tweaking.
If that's the board I think it is, it's an 11/10S. The preset was adjusted at
the factory, and you could set most standard baud rates using the switch. It
can't hurt to measure the frequency, of course.
I can check the printset next weekend for you if you can't figure it out.
--
Scott Ware s-ware(a)nwu.edu
-tony