Date: Fri, 18 Jun 1999 15:04:53 +1000 From: "Andrew Johns" <ajohns@TurnAround.com.au> To: <cjclark@home.com>, "FreeBSD Questions" <freebsd-questions@FreeBSD.ORG> Subject: RE: Null-Modem? Message-ID: <000f01beb948$1a080670$4001a8c0@tasajohns.turnaround.com.au> In-Reply-To: <199906180447.AAA07698@cc942873-a.ewndsr1.nj.home.com>
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A null-modem cable is a cable with the correct wires crossed/joined -
typically if all you want is software flow control (not the best but it
works) just connect pins 2,3 and 7 in a DB25 serial port connector (aka
V35 connector) and swap pins 2 and 3 at one end. Pin 2 is transmit, 3
receive, 7 ground; so you've got:
One end: Other end:
TX 2 --------\/------------- 3 RX
RX 3 --------/\------------- 2 TX
Gr 7 ----------------------- 7 Ground
Config your machine for software flow control (XON/XOFF) and it'll send
^S (XOFF) when it's buffer is full and ^Q (XON) when it's ready to
receive again.
If you don't have access to cables that you can hack/cut/modify, you'll
need to buy one - any decent computer shop will have them.
As for the BIOS, look for a "Halt On" option in the BIOS and change it
to Halt On "No Errors" - "All Errors" is probably the default and
"Keyboard" will probably be another option (checks for the presence of a
keyboard). Halt on "No Errors" will allow the machine to boot without a
keyboard attached. I don't know off the top of my head whether the
Phoenix BIOS has this particular option or not. Good luck...
HTH
Microsoft: Keeping brain-dead administrators in work for ever
(fixing/maintaining/rebooting it).
> -----Original Message-----
> From: owner-freebsd-questions@FreeBSD.ORG
> [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of
> Crist J. Clark
> Sent: Friday, 18 June 1999 14:48
> To: FreeBSD Questions
> Subject: Null-Modem?
>
>
> I've been considering the possibility of using some ol' Wyse terminals
> we have laying around (from the retired VAX, may it rest in peace) to
> connect one terminal head to serveral FreeBSD machines (I have a
> switch from those ol' days too).
>
> Now, I would think from a hardware end it should be as easy as
> plugging the right adapter into the terminal, run the other end of the
> wire into an adapter that nicely fits in the serial port of the
> FreeBSD machine.
>
> However, I go look at some FAQ and Handbook sources, and the term
> 'null-modem' comes up. Sometimes the context makes 'null-modem' sounds
> like what it says, null, nothing, nada. Other times, it sounds like a
> null-modem is either an adapter or special wire of some type.
>
> So, just what is a null-modem if it is anything at all?
>
>
> Oh, one thing tagged on here. There is no need for a 'regular'
> keyboard on this machine (or sc0, but I'll leave the card in there),
> but the BIOS likes to refuse to boot if no keyboard is hanging off of
> of the usual port. I was not able to find a way to turn that off in
> the BIOS setup (PhoenixBIOS). Anyone have a work-around for that? Or
> is there some obscurely named option in the BIOS setup to do that?
>
> (Just last night I was doing a RELEASE to STABLE build on a machine,
> and I forgot I had removed the keyboard before telling it to reboot
> the new kernel. Had to wait until I got to work the next day and
> crawled under my desk to plug a kb in to see if all went well. :/ )
> --
> Crist J. Clark cjclark@home.com
>
>
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