27 Mar
2020
27 Mar
'20
2:55 a.m.
John H. Reinhardt <johnhreinhardt at
thereinhardts.org> wrote:
The OPA0: port is #3 (don't ask me why)
In the VAXstation (NOT MicroVAX), starting with the 2000 family, serial ports 0 and 1
were for the keyboard and mouse. Port 2 was for the modem/communications, and port 3 was
for the printer. VAXstations didn't normally need a serial console, but if you had to
connect one for some reason the printer port was used. They couldn't use ports 0 or 1
because those were needed for the keyboard/mouse, and I guess DEC decided they wanted to
keep the modem port open. The MicroVAX-2000 and 3000s are the same hardware as the
corresponding VAXstation, and DEC kept the serial port assignments the same.
Bob
This web site has just about everything you want to know about DEC modular wiring and
their parts (plus a lot more, check out the RS-232 pages)).
<https://www.lammertbies.nl/comm/cable/dec-mmj#bc16>
--
John H. Reinhardt