Altair serial port update

Richard A. Cini rcini at
Sat Aug 6 21:13:53 CDT 2005

This is so true. I have one of those boxes on this particular system and
it at least tells me what's going on with the lines.

At this point I'm at a loss as to what's wrong. I believe that the card
works based on the loopback program. It's got to be a problem with the
loader and how the paper tape image is coming over the line from the
terminal (a laptop).

I really need someone with a known-working configuration that uses an
SSM card to let me know how it's configured. Otherwise, I'm going to
have to setup a trade for a real Altair SIO card.


-----Original Message-----
From: cctalk-bounces at
[mailto:cctalk-bounces at] On Behalf Of Tony Duell
Sent: Saturday, August 06, 2005 4:17 PM
To: cctalk at
Subject: Re: Altair serial port update

> All:
> 	Word to the wise -- always check the cabling. I've been wracking
> brain this week on the serial port problems with my Altair. I wired 
> the serial board cable per the manual but I never checked if it was 
> NULL or not. Well, when I put a null adapter on the cable, it worked! 
> Whoo, hoo.

I don't want to say how many times I've made that sort of mistake :-)

Another word to the wise... Get one of those little in-line RS232 
testers. The one I have has 7 bi-colour LEDs on it that monitor TxD,
RTS, CTS, DSR, DTR and CD. I've seen one with more LEDs too.

I'm always using mine to cheack whether an RS232 port is wired as a DTE 
or DCE. Or if it drives any of the handshake lines. I find it a lot more

use than my fancier breakout boxes, comms analysers, etc.


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