On Sun, 4 May 1997, Matt Thompson wrote:

> Hi .. does anyone know the pinouts of the 9 pin serial console port on
> the MicroVAX II? Is this a standard PC RS232 port?

---
>From deep in the archives -- port-vax.0006

> From: rick@snowhite.cis.uoguelph.ca
> Date: Mon, 26 Jun 1995 11:46:25 -0400
> Subject: MicroVAXII console
> 
> The MicroVAXII serial console port is:
> 
> 9 pin D with pinout
> 1 - grnd
> 2,3 - snd, rcv (crossed to terminal for partial null modem)
> 8 to 9 - shorted together
> (I think, I don't have a manual handy. If I'm wrong would someone please
> correct me.)
>
> The toggle switch enables/disables halt when break is pressed on the
> console keyboard
> (up is enabled)
>
> The console terminal needs to be set to 8bit, no parity and whatever
> bit rate that is set by the rotary dial switch.
>
> The other three position dial switch is usually set to the top (arrow)
> position. (the middle position is "language inquiry" for terminals that
> can handle multiple character sets and the lower position is "loopback
> test". (Loopback test of what, I don't know:-)

---

To add some confusion to my answer, I'm successfully talking to my 
MicroVAX II on a serial cable with only the following on the DB9 connector 
console port:

pin  function
---  --------
2    transmit \__ lines are crossed to the terminal 
3    receive  /
5    ground

---

In double checking with my handy RS232 reference, it would appear that
pin 5 is `signal ground' and pin 1 on the DB25 connector is `frame
ground'.  Pin 1 on the DB9 connector is listed as `DCD' -- but we are
afterall talking about DEC here.  It is quite possible that the pin 1 on
_their_ 9 pin port is `frame ground'.

[defn: frame ground - chassis ground of equipment.]

... Crap, according to my reference card on the DB25 it lists pin 2 as
transmit data, and pin 3 as receive data -- BUT on the DB9 it lists pin 3
as transmit data and pin 2 as receive data (and no it's not in reference
to a null modem cable). Now I'm confused. I'd thought that 2/3 were TD/RD
on both 9 and 25 pin connectors. Grrrr -- stupid world.

---

Okay, I'll start my answer over from what is real and in front of me and
working.  My cable consists of a DB9 female connector and a DB25 female
connector.

DB9                   DB25
-----                 -----
pin 5   is wired to   pin 7 
pin 2   is wired to   pin 3
pin 3   is wired to   pin 2

This works really well for me... but I have no idea if it will work for
anyone else as RS232 specs seem to be either fundamentally random or a
function of your location in the time-space space continuum modulo the
number of M&Ms you've eaten in your lifetime.

-brian.
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Brian D. Chase            Unix/Network Shaman          brianc@carpediem.com
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