Subject: Re: slightly-off-topic: serial ports?
To: Jacob H. Suter <jsuter@intrastar.NET>
From: Tim Shoppa <>
List: port-vax
Date: 08/05/1997 11:10:05
> Ok..  I've gotta make myself some serial cables.  I've got some VS3100's
> and some VT320-C2 (vt320 dumb terminals made by digital).  Anyone got the
> pin-outs for these ports (whats tx/rx/dts/dsr/ground/etc)...

If you can't find any MMJ plugs locally, you can either just get a
regular RJ11 and file the jack until it fits (it won't latch in)
or you can buy the plugs mail order, from places like Digi-Key
(1-800-DIGI-KEY).  I also sell complete cables.

>From the comp.unix.ultrix FAQ:

26. What are the pinouts of the MMJ jacks on the back of various DECstations
        and VAXstations?

This describes the 6-pin modified modular jack (MMJ) used for serial ports
on various DECstations and VAXstations, as well as on other DEC equipment.

DEC carries four DB-to-MMJ adaptors.  They are internally wired as follows

                   Rdy Out  TX+  TX-  RX-  RX+  Rdy In
 Adaptor   Gender     1      2    3    4    5     6       Use with:
 H8575-A     F      20      2    7    7    3    6&8     VTxxx terminal
 H8571-C     M       6      3    7    7    2     20     DEC printer
 H8571-D     M       6      3    7    7    2     20     Modem
 H8571-E     M      20      2    7    7    3    6&8     Female terminal
                                                        or LaserWriter

RS-232 using DB-25 connectors:
                                                DTE           DCE
                                             Terminal        Modem
                                            or computer
Pin Number Signal Name
    2          TD        Transmit Data                   -->
    3          RD        Receive Data                    <--
    7          GND       Ground                          ---
    6          DSR       Data Set Ready                  <--
    8          DCD       Data Carrier Detect             <--
   20          DTR       Data Terminal Ready             -->

Tim. (