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Date:      Wed, 16 Jan 2002 21:49:32 +0100
From:      Bernd Walter <ticso@cicely8.cicely.de>
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        Trevor Johnson <trevor@jpj.net>, Riccardo.Veraldi@fi.infn.it, freebsd-alpha@FreeBSD.ORG
Subject:   Re: DEC3000/300
Message-ID:  <20020116214931.M50371@cicely8.cicely.de>
In-Reply-To: <3C45DF84.5990A4E4@mindspring.com>
References:  <20020116023458.E17814-100000@blues.jpj.net> <3C45DF84.5990A4E4@mindspring.com>

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On Wed, Jan 16, 2002 at 12:16:04PM -0800, Terry Lambert wrote:
> Trevor Johnson wrote:
> > > I just got a DEC3000/300
> > > to use the seial console do I have to get a NULL modem or modem serial
> > > cable?
> > 
> > I made a quick-and-dirty null modem cable to attach to a PC:
> > 
> > DB25F         DB9F
> > (DEC 3000)    (PC)
> > 2 ----------- 2
> > 3 ----------- 3
> > 6 ----------- 6, 8
> > 7 ----------- 5
> 
> This isn't a NULL-modem cable (2&3 aren't swapped), it's just
> "a cable with pin 8 hooked to pin 6 on one side for some reason".

You overlooked that one side is DB-9 and the other DB-25.
But the bridging of 6 and 8 (CTS and DSR) is questionable.

> A real NULL-modem cable looks like:
> 
>  TX -------- RX
>  RX -------- TX
> CTS -------- RTS
> RTS -------- CTS
> GND -------- GND (signal ground, not chassis ground)
> DCD -------- DTR
> DTR -------- DCD
> GND -------- (chassis ground on one end to all other wires)

I usually additionaly bridge DSR with DCD on both sides just in
case I need to use it for designs requiring DSR.

-- 
B.Walter              COSMO-Project         http://www.cosmo-project.de
ticso@cicely.de         Usergroup           info@cosmo-project.de


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