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Re: Serial cable pinout??

> On Thu, 19 Dec 1996, David Puryear wrote:
> > I'm trying to connect two computer with serial cable but I couldn't find
> > the cable long enough. So I went to electronic store and bought cable
> > without plugs and plugs. I ask them which wire went where, but they had
> > no idea.:( I think I saw a posting of this somewhere, but have no idea

> One solution is to simply make your cable with the one-to-one mapping of
> pins and simply buy a null modem adapter to swap the pins.  If you want to
> hard wire the change into your cable, I've got a null modem that I've
> opened up here.  It looks like pins 2 and 3 have been interconnected. 
> Pins 4 and 5 on a given connector are tied together, and go to pin 8 on
> the opposite connector.  Pin 6 is tied to pin 20.  I would try to verify
> this with someone else though just to be sure.

Hmmm. This would probably work, but I wouldn't recommend it for
terminal use; I think it's the sort used for a laplink serial cable.
Pins 2 & 3 are TX and RX respectively, so they must be swapped.
4 & 5 are RTS and CTS flow control, 8 is DCD off the top of my head.
So turning on RTS turns on CTS and DCD. Pin 6 is DSR, 20 is DTR.

The problem with this is that if you're using RTS/CTS flow control,
when RTS gets dropped, so does DCD, and your getty will log you out.
I think DTR/DSR flow control would work, but this is a bit
more unusual.

I recommend the following;
2 -> 3, 3 -> 2: TX to RX, RX to TX
4 -> 5, 5 -> 4: RTS to CTS, CTS to RTS
6, 8 -> 20, 20 -> 6, 8: DTR to both DSR (data set ready) and DCD.
7 -> 7; ground.

I've used this for a terminal connection with Linux and it works
fine. I believe it works with Laplink-type programs too.


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