Serial port problems on 6300

[The Wumpus]

In article <2742 at sfsup.UUCP> jerry at sfsup.UUCP (Jerry Theisen) writes:
>I have an AT&T PC 6300 that has worked without a problem for 2 and a half
>years.  Now for some reason, the serial port has up and died.
>These are the symptoms:
>
>	I hook up a modem (AT&T 4000) and an rs232 cable.
>	I enter my communication program (ctrm).
>	As I enter characters the transmit light on the modem blinks, but
>	   nothing is echoed on the screen, and indeed the
>	   receive light on the modem (those that have one) never
>	   blinks.  And I cannot get the usual modem prompts.
>
>I tried installing another serial port, but can't get the 6300 to recognize
>it.  Is there a dip switch somewhere that I set to tell the 6300 that
>there are 2 serial ports installed?  If not, should it automatically
>recognize the additional port?  Is there a way to simply disable the
>primary port?


The first question is "Did the problems start to occur just after
adding a board to your computer?"  If so, the problem is not the
serial port, but the interrupt structure of the hardware you are
using.  There are a fixed number of interrupt lines that can be used
by hardware.  Some of these lines are already used by the 6300's
onboard parrellel and serial ports.

Since you say you tried to install another serial port, was it before
or after the problems started. If it was before, the problem is in how
the serial board is configured.  Check your documentation on the
serial board and make sure the board is set up to be COM2:.  The
change would be done on the board and will probably involve moving
jumpers.

If you installed the serial board after the problems started and
installed another board before the problems started, check to make
sure that the other board is not trying to use the same interrupts as
COM1: (the 6300 serial port).  The information on the interrupts that
the board is using should be in the manual.  A simple way to check if
the interrupt problems were caused by a new board is to remove the
board ans see if the built in serial port works.

There is no switch on a 6300 to tell it the number of serial ports you
are using.  The hardware and software will recognize the number of
ports if they are configured each as a seperate port  (ie. 1 serial
port is COM1:, the next is COM2:).  I know of no way to disable the
onboard serial port.

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