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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
> as where. So I'm sorry if this is wrong place, but I don't know where to
> ask this. I asked all the computer stores around here and they don't
> know it either. One of them did say 2 and 3 are reversed, but didn't
> know anymore details. Does any one know the pinout of 9 pin serial
> cable?

The problem is that the RS232 serial line has two device types.  If I
remember this correctly:  Data Communication equipment (DCE) and Data
Terminal Equipment (DTE).  When connecting something like a computer and
modem together you don't interchange any of the wires.  Since the send pin
on one matches the recieve pin on the other.  The wires only need switched
when connecting two pieces of equipment of the same type together, which
it sounds like you are doing.

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.

Hope it helps.

- Wayde Allen

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