for DOS CTTY command, what pins do I need?

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2 total messages Started by Lou Glassy Tue, 07 Apr 1992 18:40

#131

Author: Lou Glassy
Date: Tue, 07 Apr 1992 18:40

53 lines
2012 bytes

Hello, all.

I've been trying to hook up a standard terminal to a PC through
the COM1 port using the dos CTTY command.  So far, no luck.  I've 
tried all manner of MODE settings for the com port, so far to no avail.
After doing the MODE command, as in

   MODE COM1:9600,n,8

I do a CTTY COM1

then get either something like

   ERROR WRITING DEVICE COM1 (ABORT RETRY IGNORE FAIL)?

or nothing at all.  The PC just hangs, and won't do anything else 
until it's been rebooted.

To connect the PC to the terminal, I've been using a DB9-to-DB25
cable (DB9 on the PC side, DB25 on the terminal side).  With a breakout
box, I've switched lines 2 and 3 on the terminal (DB25) end of the
cable.

Some different things I've tried are:
   - terminal and PC at 1200, 2400, 9600 baud
   - parity on and off, even or odd
   - 8/7 bits per character at both ends, with 0/1/2 stop bits.

and so far, nothing has worked.  The suspicion I've got, is that
something's wrong with the handshaking.

When I disassembled a terminal connector attached to the 
campus network, the only lines present in the terminal-end
DB25 were
   2  - red
   3  - green
   7  - black
   20 - green

Question:  what lines on the DB25 end of the DB9->DB25 connector
do I need to jumper together to get CTTY to work?

(The hardware I've been trying all this stuff on, is a DEC 386sx-16
for a PC, and an Ergo 301 MicroTerm (a vt100-clone) for a terminal.)

Thanks in advance,

Lou.

-- 
               "Open the pod bay doors, Hal."

            icsu8209@cs.montana.edu :: Lou Glassy

Re: for DOS CTTY command, what pins do I need?

#139

Author: Steve Madsen
Date: Thu, 09 Apr 1992 17:07

30 lines
1794 bytes

> I've been trying to hook up a standard terminal to a PC through
> the COM1 port using the dos CTTY command.  So far, no luck.  I've 
> tried all manner of MODE settings for the com port, so far to no avail.
> 
> When I disassembled a terminal connector attached to the 
> campus network, the only lines present in the terminal-end
> DB25 were
>    2  - red
>    3  - green
>    7  - black
>    20 - green

        My guess for the solution to this problem would be to make sure that
your DTR (data terminal ready) and the DCD (data carrier detect) lines are both
asserted (high) when you issue the CTTY command.

        I used this command to kludge a "shell to DOS" command for a BBS I ran
for my old high school last year, and this command was only used during an
online session when both DTR and DCD were high (since someone was calling in). 
This seems to make sense because CTTY needs to make sure that things it sends
can actually go out the port (which is only possible when DTR is high).

-- 
Steve Madsen       !  Internet: sjmadsen@miavx1.acs.muohio.edu  (preferred)
Miami University   !    Bitnet: sjmadsen@miavx1
Oxford, Ohio       !

"VAX.  For those who care enough to steal the very best."  -- A microscopic
  message on the silicon chip inside one of Digital Equipment's often stolen
  computer designs.

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