Newsgroups: comp.sys.att
Subject: Re: Need source for 3B2->DB-25 adapter.
From: rthomas@hakatac.almanac.bc.ca (Robert N Thomas)
Date: Fri, 18 Dec 92 08:34:53 GMT
Organization: Sir HackAlot's Castle BBS, Port Alberni, B.C., Canada

In article <1fpbl6INN452@tamsun.tamu.edu> jfrench@cs.tamu.edu (Jeff French) writes:
>I have a 3B2 with no way to attach a terminal to it. What is a good
>source of DB-25 shell connector to 3B2 whatever-the-hell-you-call-it
>port connectors. If the pinout is commonly available, I could make it
>myself. I would sure hate to have to wade through the red tape of ordering
>such a small part from AT&T. Tips, clues, flames, all are appreciated. I
>checked FAQ to no avail.

   Looking into the 8 pin modular jack (RJ45 I think??) you'll see that 
pin 1 should be on the right..

       Diagram of what you should see when looking at an 8 PIN
               modular jack connector..

               +----------+
               | 87654321 | 
               |          |
               +--+    +--+
                  |    |
                  +----+

  Ok, not all 3B2 8 pin modular jack connectors are created "EQUAL"..  These
beasties are used for running StarLan 1MBit, EPORTS cards, PORTS cards, as
well as for running ETHERNET 10MBits as well..

  The pin outs for the 2 modular jack cables on the back of the 3B2,
as well as for the PORTS card should be as follows....


     PIN     Lead           Direction             Explanation
    =====  ==========     =============         ========================
      1     PROT GRD                              Ground
      2     reserved                              Not Connected
      3     TXD0            Out                   Transmit Data
      4     DTR0            Out                   Data Terminal Ready.
      5     RXD0            In                    Receive Data
      6     DCD0            In                    Data Carrier Detect
      7     SIG GRD                               Signal Ground
      8     reserved                              Not Connected


    The 2 modular jacks on the back of your machine should be labeled console
and contty.  If your talking about a PORTS card, here is what one looks like...

     Centronics connector
     for Parallel Printer
          |
         \|/
     +------------+     +----+    +----+    +----+   +----+
      \          /      |    |    |    |    |    |   |    |
        \_______/       +----+    +----+    +----+   +----+

                           ^         ^        ^        ^
                          The above 4 RJ45 connectors are for
                        plugging serial terminals into your 3B2.


     The EPORTS card is card that has 8 RJ45 connectors (8 pin modular jacks)
on it.  This card is where you would want to plug a modem onto your system,
because the above connectors DO NOT SUPPORT HARDWARE FLOW CONTROL..  
The PIN OUTS for the EPORTS card is as follows....


   
     PIN     Lead           Direction             Explanation
    =====  ==========     =============         ========================
      1     PROT GRD                              Ground
      2     CTS             Out                   Clear to Send
      3     TXD0            Out                   Transmit Data
      4     DTR0            Out                   Data Terminal Ready.
      5     RXD0            In                    Receive Data
      6     DCD0            In                    Data Carrier Detect
      7     SIG GRD                               Signal Ground
      8     RTS             In                    Request to send



* NOTES:

CTS & RTS (if you have them)..
          Most 3B2 systems need to do the following to enable hardware flow
     control..  Otherwise the 3B2 will ignore RTS & CTS.

        epstty hfc    <-- XON/XOFF flow control must be disabled before you
                        do this..  stty command is 1 way to disable XON/XOFF.
                        Line DISCIPLINES are another way to do this..
                           see etc/gettydefs file..


DTR0 notes.. {3b2 uses this to signal DISCONNECT}

         When the 3B2 is active on the port  (waiting for someone to logon
to the port or whatever..), DTR is active..   When the 3B2 wishes to
DISCONNECT (ie too many wrong passwords, or the user logs off the port),
it will lower DTR momentarily.  If you are trying to get a modem to work, you
might want the modem to DISCONNECT the user when DTR is dropped..



DCD0 notes.. {Used to tell 3B2 that the user has DROPPED CARRIER}

         When the DCD is set inactive, the 3B2 will assume that the user
has either turned off the terminal, or dropped carrier.  If this occurs,
the user is logged off the system, and background tasks are aborted..
If DCD is inactive, be aware that NONE of the standard AT&T provided utilities
are capable of sending anything to the device.
{cu won't work on the device, and forget about outbound UUCP's from working}

    In the case of a MODEM, when the user drops carrier, you want the modem to
"momentarily" lower this DCD0 just long enough for the 3B2 to realize that the
user has dropped carrier.  The modem should then Re-ENABLE DCD0, so that the
3B2 will be able to send data to the modem.  {needed for cu, and outbound
UUCP to work correctly}

     Most semi-decent modems are capable of handling DCD and DTR in a 3B2
friendly manner.  I have done this with PEP's, USR HST's, and MicroComm
9600 AX modems, without incident..

This is probably a useful blurb for the FAQ..

Cheers....

						---- Robb ----