Subject: Re: Getting qbus async mux working.
To: Ronny Svedman <ronny@Update.UU.SE>
From: Ken Wellsch <>
List: port-vax
Date: 09/05/1998 09:55:16
> I want to plug an extra VT320 into one of the eight rs232:S at the back of
> my microvaxII. it would be nice to have another terminal besides the
> console vt420. Now my question is:
> What devices do i need to make (The mux board is a DEC original, marked
> M3104) ?
> how do I check if they work? (I.e: can I just try cat:ing things on teh
> raw tty devices and se if anything happens onm teh VT, and THEN start
> worrying about gettys and stuff?)

It has been a long time, but I think an M3104 is a DHV board.  When your
system boots does it mention a dhv unit? Take a look in /dev/MAKEDEV to
see what the tty names are for a DHV. I think they are of the form
/dev/ttyS[0-7].  As for simply catting data at the raw port, I vaguely
recall you can run into hand-shaking problems - you get hung waiting
for an RS232 signal or other.  Maybe not, but I think you'd be safe to
just go edit /etc/ttys and enable say /dev/ttyS0 then "kill -1 1" to
fire-up a getty - then go plug your VT320 into each port until you find
0 (assuming you don't already know where it is). I believe you'll get
a login banner on connection as the driver detects the signal state change
and the getty gets revived.  Otherwise hit the old <RETURN> key and look
for a banner if none appears when the cable is attached.  -- Ken