4 Aug
1997
4 Aug
'97
1:18 a.m.
On Sun, 3 Aug 1997, PDP11 Hacker ..... wrote:
(regarding the BERG connector on the M9970 module in a PDP-11/10)
It's the standard DEC serial connector. Current
loop is certainly there, and I
think at least one of the TTL and/or EIA connections are there as well. This
may depend on which CPU board set you have, however. I seem to recall
pinouts/cable lists are on one of the PDP_8_ web sites.
Great! I've already found the pinouts, and I'll check voltages as soon
as I power the machine up.
11/10's use an RC clock for the baud rate
generator. It's tweakable by a
preset on one of the boards - check it at pin 40 of the UART (the only
40 pin chip in the CPU), and set to 16 times the baud rate. I think the
11/10S uses an Xtal clock, and there's a switch to set standard rates.
The RC clock does 110 baud as standard, but can be tweaked at least to
300 baud. You can change (reduce) the timing capacitor to get higher
rates, of course.
-tony
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.
--
Scott Ware s-ware(a)nwu.edu