From owner-freebsd-stable  Thu Jun 14 12:48:47 2001
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Date: Thu, 14 Jun 2001 12:48:24 -0700 (PDT)
From: Matt Dillon <dillon@earth.backplane.com>
Message-Id: <200106141948.f5EJmOe28264@earth.backplane.com>
To: David Miller <dmiller@sparks.net>
Cc: freebsd-stable@FreeBSD.ORG
Subject: Re: serial port stuck at 9600
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:configured with the com port on "auto".  When set to be com1 at IRQ 4 it
:ceased to function at all, matching the other two systems.
:
:I've tracked the problem down to the port (ttyd0) not having DCD
:input.  Using cuaa0 worked fine, so the serial port is OK.
:
:I checked the cable, and DCD is wired straight through (pin 1 on the 9 pin
:ports), so it's not the cable.

    That is the cable... when building a null modem cable DTR is supposed to
    be wired to DCD and vise versa.  It should be something like:

    DTR	-> DCD
    DTR -> DSR
    DCD <- DTR
    DSR <- DTR
    RTS -> CTS
    CTS <- RTS
    TX  -> RX
    RX  <- TX
    SGND<-> SGND

					-Matt
 
:I'm connecting with a serial port on another PC running freebsd and "cu -l
:/dev/cuaa0 or cu -l /dev/ttyd0".  In both cases I get a connection
:message, but the remote end never responds.  I slapped a breakout box on
:the end of the cable and confirmed that DCD is not being raised by cu.
:
:That means my question is: "When using a FreeBSD system as a console for
:another system, how do I raise DCD in order to establish a connection?"
:
:Clues welcomed:)
:
:--- David

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