                       10BaseT 

  This document contains 10BASE-T cabling information and the pinout 
  for the RJ-45 connector.  For more information on the 10BaseT
  specification contact your local network supplier or call the 
  IEEE (800-678-IEEE).

  NOTE: This document or an updated version is available on FaxBACK. 
        (Document #6202)

INTRODUCTION:
-------------

  A 10BASE-T cable from the network card to the hub should be a
  straight through unshielded twisted pair cable.  A typical problem
  with 10BASE-T is a crossed wire in the cable or wiring closet.  If
  you experience problems where a hub cannot "see" a workstation, check
  to make sure the wiring is correct.

  To allow for a straight through cable, the hub provides an internal
  transmit/receive crossover function.  This means the transmit circuit
  of the network card is connected to the receive circuit of the hub
  and vise versa.

               Function    Pin#               Pin# 
              -------------------------------------
                 TX+        1    <--------->   1   
                 TX-        2    <--------->   2   
                 RX+        3    <--------->   3   
                 RX-        6    <--------->   6   
              -------------------------------------
                      STRAIGHT THOUGH CABLE

  Even though there are eight pins on a 10BASE-T connector, only four
  are used (pins: 1 and 2 should be a pair, 3 and 6 should be a pair).

  The RJ-45 connector can support unshielded twisted pair (UTP) cable
  of 22, 24, or 26 gauge.  The cable must comply with the IEEE 802.3
  10BASE-T standard with the maximum distance between the computer and
  the hub being 100 meters.

  Silver satin is not within the 10BASE-T specification and cannot be
  used.  If used, it may not work at all, or may give intermittent
  results.


PRE 10BASE-T:
-------------

  If you're in a Pre10BASE-T environment, you'll need to use the AUI
  connector on the EtherExpress card with a transceiver.  The
  transceiver must be setup for Pre10BASE-T (link integrity off).


LINK INTEGRITY:
---------------

  For 10BASE-T networks, Link integrity (LI) needs to be on.  Some
  transceivers, ethernet cards, or other network devices allow you to
  turn it off, but Link Integrity is always on with the EtherExpress
  cards.

  If you're using a transceiver to go to a thick/thin ethernet segment,
  Link Integrity must be set to on for the transceiver.


POLARITY PROBLEMS:
------------------

  Another problem in 10BASE-T wiring is crossing the positive and
  negative phases of the transmit or receive signals.  For example, a
  problem would occur if pins 1 and 2 were crossed.  (TX+ connected to
  TX-).

  Some 10BASE-T network adapters can automatically detect this problem
  an adjust for it internally.  Early EtherExpress 16 TPs did not have
  this feature, but the current EtherExpress 16 TP and EtherExpress 
  MCA TP do.

  Even though the current EtherExpress adapters can take care of this
  crossover for you, it is best to check your wiring and correct this
  problem if you find it.

  If your workstations are having problems connecting, reset or power
  off/on your concentrator or hub.


CONNECTING TWO WORKSTATIONS WITHOUT A HUB:
------------------------------------------

  10BASE-T uses a star topology.  This means there is a hub or
  concentrator is in the center of a star and each workstation or server
  is connected to this hub.
 
  For test purposes, you can connect directly connect two workstations
  or a workstation and a server without using a hub.  This requires a
  special cable that incorporates the crossover function talked about
  at the being of this document.

            Function    Pin#               Pin#   Function
           --------------------------------------------------
              TX+        1    <--------->   3        RX+
              TX-        2    <--------->   6        RX-
              RX+        3    <--------->   1        TX+
              RX-        6    <--------->   2        TX-
           --------------------------------------------------
                           CROSSOVER CABLE  



PINOUT FOR RJ-45 CABLE CONNECTOR:
---------------------------------

            ----------              --------------------------
         1 |--        |          1 |------------              | 
         2 |--        |          2 |------------              |
         3 |--         ---       3 |------------              |
         4 |--            |      4 |------------              |
         5 |--            |      5 |------------              |
         6 |--         ---       6 |------------              |
         7 |--        |          7 |------------              |
         8 |--        |          8 |------------              |
            ----------              --------------------------
               END                             TOP

  PIN  NAME AND FUNCTION
  1    Transmit Data Plus.  The positive signal for the TD differential
       pair.  This signal contains the serial output data stream
       transmitted onto the network.

  2    Transmit Data Minus.  The negative signal for the TD differential
       pair.  This contains the same output as pin 1.

  3    Receive Data Plus.  The positive signal for the RD differential
       pair.  This signal contains the serial input data stream received
       from the network.

  4    not connected

  5    not connected

  6    Receive data minus.  The negative signal for the RD differential
       pair.  This signal contains the same input as pin 3.

  7    not connected

  8    not connected


PINOUT FOR AUI PORT:
--------------------
                          shell = protective ground
                                               |
          ---------------------------------------------
          |       o   o   o   o   o   o   o   o       |
           \      1   2   3   4   5   6   7   8      /
            \                                       /
             \      o   o   o   o   o   o   o      /
              \     9  10  11  12  13  14  15     /
                ---------------------------------

  PIN  NAME AND FUNCTION
   1   Control-in Shield.  The shield for the CI twisted pair on the 
       AUI cable.

   2   Control-in Circuit A.  The positive signal for the CI circuit.
       This circuit is used to send the mau_available and
       signal_quality_error messages to the equipment.

   3   Data-out circuit A.  The positive signal for the DO circuit.

   4   Data-in Shield.  The shield for the DI twisted pair in the AUI
       cable.

   5   Data-in Circuit A.  The positive signal for the DI circuit.

   6   Voltage Common.  The ground return for the VP circuit.

   7   not connected

   8   not connected

   9   Control-in Circuit B.  The negative signal for the CI circuit.
       This circuit sends the same signals as listed under pin 2.

   10  Data-out Circuit B.  The negative signal for the DO circuit.

   11  Data-out Shield.  The shield for the DO twisted pair in the AUI
       cable.

   12  Data-in Circuit B.  The negative signal for the DI circuit.

   13  Voltage Plus.  The power supply to the transceiver.  The supply
       must remain in the range of 12V - 6% to 15V + 5%.

   14  Voltage Shield.  The shield for the VC and VP (pins 6 and 13)
       twisted pair.

   15  not connected
