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Re: Problem w/ serial console after power-on

Subject: Re: Problem w/ serial console after power-on
From: Karsten Merker <>
Date: Wed, 11 Oct 2000 07:48:50 +0200
In-reply-to: <>; from Jan-Benedict Glaw on Wed, Oct 11, 2000 at 01:38:04AM +0200
References: <>
On Wed, Oct 11, 2000 at 01:38:04AM +0200, Jan-Benedict Glaw wrote:

> I've got a DECStation 5000/120 and tried to start some hacking,
> but no success: I can read everything the box outputs to its
> serial lines, but anything I type into my minicom seems to end
> up in /dev/null... The cable is okay, but what could be wrong
> instead? Any hints?

Well known effect :-)
I have a "normal" 7-wire-nullmodem cable that works fine when connecting
my vt420 to my Linux PC and running a getty on the port, ist also works
fine when connecting the vt420 to the DECstations serial console port, but
I have the same problem as you when connecting the DECstation to the PC
and running a terminal emulation program on the PC.

The soloution: use a 3-wire-nullmodem cable and inside each of the
connectors connect RTS-CTS and DTR-DSR-DCD.

This should look like this:

DECstation           PC

GND ---------------- GND

RxD ---------------- TxD

TxD ---------------- RxD

RTS -+            +- RTS
     |            |
CTS -+            +- CTS

DTR-+             +- DTR
    |             |
DSR-+             +- DSR
    |             |
DCD-+             +- DCD

Viel Spass beim Loeten :-).

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