Subject: Re: Q: fake Terminal with MMJ plug alone?
To: Wolfgang Rupp , <port-vax@netbsd.org>
From: Chris Tribo <ctribo@del.net>
List: port-vax
Date: 06/07/2001 00:13:56
on 6/6/01 5:54 PM, Wolfgang Rupp at rupp@chello.at wrote:

> 
> The subject says it. I want to put my MV3100 into an ISP rack as a
> webserver. The drawback is that normally there must be a terminal
> connected, or the machine won't boot. Later, the terminal can be
> unplugged without problem (but not switched off -> instant crash).

    If memory serves, this is not a crash. When you power off a terminal it
usually will sent a "break" "signal" to the computer it's attached to. That
being the case, the computer isn't crashed, just stopped. I think you can
type "continue" into the >>> and it will go back to running the OS.
(assuming that a break is really what it's recieving and not crashing.)

> As I understand, the terminal has some kind of "I'm here" signal.
> Can this be faked by soldering some wires of an MMJ plug together,
> or can it otherwise be faked?

    As was mentioned in another post, the VAX wants to see a DTR (data
terminal ready) signal high before it'll receive (and possible send)
information to you. By connecting DSR to DTR you are taking the high signal
coming from the VAX and looping it back into it so neither terminal nor VAX
knows the wiser. While not having tried it, I think if you can set up your
terminal not to send a break a power off, you wouldn't need to do this, or
it wouldn't make any difference if it is indeed sending a break. One of the
VAX gurus here probably knows more on the ins and outs of this stuff than I
do.


    Chris