### EtherLite Cable Guide

RJ-45 Cabling/Pinouts

RS-422/485 Implementation

RS-232 Definitions

Connectors and Pinouts

- DTE to DTE Null Modem Pinouts
- DB-25 Connector Pinouts
- DB-9 ( PC-AT-style) Connector
- RJ-45 Connectors
- RS-422/485 Connector
- RS-485 (EtherLite 2 only)
- RS-232 Connector
- Full-handshaking Null-modem Connector
- No-handshaking Null-modem Connector
- Possible Printer Null-modem Connector

#### RJ-45 Cabling/Pinouts

Important: The EtherLite RJ-45 8-pin configuration is not compatible with the pin configuration of the RJ-45 (usually 10-pin) connectors on all other Digi products. You must get or make the correct cables (shown below) for the EtherLite products to work as expected. Pre-configured cables for EtherLite products are available via Digi Sales. Be sure to get the correct cables when ordering.

#### RS-422/485 Implementation

##### RS-485 Multidrop

Only "4 wire" Master/Slave configurations are supported since the buffers are always enabled EtherLite products. In other words, transmit (TxD) pair is connected to all the slave device's receive (RxD) pairs, and the chain of slaves all have their TxD pairs connected to EtherLite and arbitrate normally for the "right to talk". In this configuration, the EtherLite termination switch should only be enabled (down position) if the EtherLite unit is at the end of the chain.

##### RS-422 Point-to-point

Termination is enabled when the termination switch is in the down position. RS-422 is enabled when the termination switch is in the up position. This puts a 120 Ohm 1/2 Watt resistor across the receive pair.

##### Notes

- It is important to understand that due to limitations in EtherLite design options, the RS-422 and RS-422 termination switches have opposite positions for their respective "enabled" position.
- Even when a port is set to RS-422 mode, signals RTS (pin 1), DCD (pin 3), and CTS (pin 8) are still RS-232 single-ended signals. Ground also remains at pin 6.

#### RS-232 Definitions

Signal | Description
TxD | Transmit Data | An output for DTE devices and an input for DCE devices. This is the data channel from the DTE device to the DCE device.
RxD | Receive Data: | An input for DTE devices and an output for DCE devices. This is the data channel from the DCE device to the DTE device.
RTS | Request To Send: | An output for DTE devices and an input for DCE devices. This signal is typically used to gate flow from the DCE device to the DTE device. In other words, the workstation serial port would drop this signal to halt flow from the modem, and then later raise it to resume flow.
CTS | Clear To Send: | An input for DTE devices and an output for DCE devices. This signal typically is used to gate flow from the DTE device to the DCE device. In other words, a modem may drop this signal to halt flow from the workstation, and then later raise it to resume flow.
DSR | Data Set Ready: | An input for DTE devices and an output for DCE devices. This signal is not widely used in UNIX, except on some DEC machines, which will block on open if it is not true in some cases.
GND | Signal Ground: | The signal return for all signal lines.
DCD | Data Carrier Detect: | An input for DTE devices and an output for DCE devices. This signal is used to show that there is a valid connection between the DTE and DCE devices. It is typically used to block opens on a port before connections, and to generate UNIX "hang up" signals upon loss of a connection.
DTR | Data Terminal Ready: | An output for DTE devices and an input for DCE devices. This signal is typically used in UNIX to show that the port has been activated or "opened".

#### Connectors and Pinout Information

##### DTE to DTE Null Modem Pinouts

Sample DTE to DTE "null-modem" wirings

##### DB-25 Connector

EtherLite products use the standard DTE pinout for DB-25 connectors, but female connectors are used to avoid possible pin shorts.

The following connector is used for products such as ST-1616, ST-1002, and ST-1008.

                                 +--------------------------+
                                  | pin | signal | direction |
          Female DB-25 DTE        |--------------------------|
                                  |  2  |  TxD   |    out    |
            ___________           |  3  |  RxD   |    in     |
           ( 13......1 )          |  4  |  RTS   |    out    |
            \ 25...14 /           |  5  |  CTS   |    in     |
             `-------'            |  6  |  DSR   |    in     |
                                  |  7  |  GND   |    n/a    |
                                  |  8  |  DCD   |    in     |
                                  | 20  |  DTR   |    out    |
                                  +--------------------------+

##### DB-9 (PC-AT-style) Connector

                               +--------------------------+
                                | pin | signal | direction |
      Male AT-style DB-9 DTE    |--------------------------|
                                |  1  |  DCD   |    in     |
            ___________         |  2  |  RxD   |    in     |
           ( 1.......5 )        |  3  |  TxD   |    out    |
            \ 6.....9 /         |  4  |  DTR   |    out    |
             `-------'          |  5  |  GND   |    n/a    |
                                |  6  |  DSR   |    in     |
                                |  7  |  RTS   |    out    |
                                |  8  |  CTS   |    in     |
                                |  9  |  RI    |    in     |
                                +--------------------------+

#### RJ-45 Connectors

Digi uses its own RJ-45 pin configuration, which is noted where appropriate below. To avoid confusion, an ASCII representation of an RJ-45 receptacle (the female connector similar to the ones used on the Digi units) is shown below with pin numbering.

This connector is used with products such as the Digi EtherLite products.

##### RS-422/485 Connector

                               +--------------------------+
        1 2 3 4 5 6 7 8         |     | RS-422 |           |
     .--+-+-+-+-+-+-+-+--.      | pin | signal | direction |
     |  | | | | | | | |  |      |--------------------------|
     |    R-  R+T+  T-   |      |  1  |  RTS * |    out    |
     |                   |      |  2  |  RxD-  |    in     |
     |                   |      |  3  |  DCD * |    in     |
     |                   |      |  4  |  RxD+  |    in     |
     |                   |      |  5  |  TxD+  |    out    |
     '-----.       .-----'      |  6  |  GND * |    n/a    |
           |_     _|            |  7  |  TxD-  |    out    |
             |   |              |  8  |  CTS * |    in     |
             '---'              +--------------------------+

##### Notes:

- These signals are always RS-232 (single-ended) even when the port is set to RS-422 mode.
- For point-to-point connections such as a direct single terminal connection, you should use the following connection scheme:

                     .---------------------.
                      | CD RJ-45 | Terminal |
                      |----------+----------|
                      | RxD- (2) | TxD- (?) |
                      | RxD+ (4) | TxD+ (?) |
                      | TxD- (7) | RxD- (?) |
                      | TxD+ (5) | RxD+ (?) |
                      `---------------------'

##### RS-485 Connector (EtherLite 2 only)

                     +------------------------------------+
                      |RJ-45|              |               |
                      | pin |    Signal    |   Direction   |
                      |------------------------------------|
                      |  1  |  No connect* |               |
                      |  2  |  No connect* |               |
                      |  3  |  No connect* |               |
                      |  4  |  TX(A)RX(A)  | Bidirectional |
                      |  5  |  TX(B)RX(B)  | Bidirectional |
                      |  6  |  GND         |               |
                      |  7  |  No connect* |               |
                      |  8  |  No connect* |               |
                      +------------------------------------+
                      *Do not connect any signal.

Note:

- EtherLite 2 RS-485 ports are wired for half duplex multiple drop EIA-485 mode and have no termination installed.

##### RS-232 Connector

                               +--------------------------+
        1 2 3 4 5 6 7 8         |     | RS-232 |           |
     .--+-+-+-+-+-+-+-+--.      | pin | signal | direction |
     |  | | | | | | | |  |      |--------------------------|
     |                   |      |  1  |  RTS   |    out    |
     |                   |      |  2  |  DSR   |    in     |
     |                   |      |  3  |  DCD   |    in     |
     |                   |      |  4  |  RxD   |    in     |
     |                   |      |  5  |  TxD   |    out    |
     '-----.       .-----'      |  6  |  GND   |    n/a    |
           |_     _|            |  7  |  DTR   |    out    |
             |   |              |  8  |  CTS   |    in     |
             '---'              +--------------------------+

Here are a few sample wiring configurations to help configure cables when adapting between Digi RJ45, and DB-25 or DB-9 connectors. These charts may also be used to configure any kind of adapter between EtherLite RJ-45, a DB-25, or a DB-9 connections, but you may need to reorganize the data. It may help to draw your own "map" before committing the pins in your connector.

                             +-----------------------------------+
                              | RJ-45 |  RS-232   || DB-25 | DB-9 |
    The standard DTE adapter: |  pin  |  signal   ||  pin  | pin  |
    ------------------------- |-------------------||--------------|
    To make an adapter that   |   1   | RTS (out) ||   4   |  7   |
    would simply give you     |   2   | DSR (in)  ||   6   |  6   |
    a standard DTE DB-25      |   3   | DCD (in)  ||   8   |  1   |
    for direct connect with   |   4   | RxD (in)  ||   3   |  2   |
    modems, use this          |   5   | TxD (out) ||   2   |  3   |
    configuration.            |   6   | GND (n/a) ||   7   |  5   |
                              |   7   | DTR (out) ||  20   |  4   |
                              |   8   | CTS (in)  ||   5   |  8   |
                              +-----------------------------------+

Note: The above adapter is actually converting signals between different connectors. No signal crosswiring is taking place.

                              +---------------------------------------------+
                              | RJ-45 |  RJ-45    ||   DST*   |DB-25 | DB-9 |
    The custom DCE adapter:   |  pin  |  signal   ||  signal  | pin  | pin  |
    ------------------------- |-------------------||------------------------|
    To make an adapter that   |   1   | RTS (out) || CTS (in) |  5   |  8   |
    would allow you to        |   2   | DSR (in)  ||  ------  | n/c  | n/c  |
    directly connect to       |   3   | DCD (in)  || DTR (out)| 20   |  4   |
    terminals and most        |   4   | RxD (in)  || TxD (out)|  2   |  3   |
    printers, use this        |   5   | TxD (out) || RxD (in) |  3   |  2   |
    configuration.            |   6   | GND (n/a) || GND (n/a)|  7   |  5   |
                              |   7   | DTR (out) || DCD (in) |  8   |  1   |
                              |   8   | CTS (in)  || RTS (out)|  4   |  7   |
                              +---------------------------------------------+

##### Notes:

- In the previous diagram, DST refers to the signal on a normal DB-25 or DE-9 DTE connector which would end up being connected to the Digi RJ-45 signal as a result of the above pinouts. In other words, the first line says that the RTS signal would be connected to the CTS signal of a terminal (or other DTE device) with pin 1 at the RJ-45 connected to pin 5 of a DB-25 shell or pin 8 of a DB-9 shell.
- Make sure to use a straight through (one-to-one) RJ-45 cable. Most TELCO modular cables are flipped from end to end, and do not work with Digi products. This means pin 1 is connected to pin 8, pin 2 to pin 7, etc.. Sometimes, the straight-through cables are also called data cables. Just make sure pin 1 at both ends is on the same wire, as well as pin 2, etc.
- Use caution with Ethernet cables for RS-232 connections. Ethernet, or category x (such as cat 5) cable has twisted pairs, and is not designed for use with a single-ended interface such as RS-232.

  If you use this type of cable with Central Data's connectors, among other things, RxD (receive) and TxD (transmit) will be twisted together, and be subject to crosstalk interference. The net result is that reliability decreases as cable length and/or baud rates increase.

  There is a way to use Cat 5 cable with modular RS-232, but you have to do some special wiring. First, you have to know which wires are twist pairs. One wire in each twisted pair (of four total) must be grounded. This means you only have 4 actual RS-232 signals you can use, but the configuration will be very reliable. Most people opt to run RxD, TxD, DTR, and DCD. This does everything except hardware flow control, which is fine for most terminals and serial printers.

#### Full-handshaking Null-modem Connector

    (DTE)           (DTE)
    -----           -----
     SG  ----------- SG
     TxD ----------- RxD
     RxD ----------- TxD
     RTS ----------- CTS
     CTS ----------- RTS
     DSR --+
     DCD --+-------- DTR
     GND ----------- GND
     DTR --------+-- DSR
                 +-- DCD

    Example pin connections:
    ------------------------

    DB-25 -> DB-25                CD RJ-45 -> DB-25
    --------------                -----------------
        2 -> 3       TxD - RxD          5 -> 3
        3 -> 2       RxD - TxD          4 -> 2
        4 -> 5       RTS - CTS          1 -> 5
        5 -> 4       CTS - RTS          8 -> 4
        7 -> 7       GND - GND          6 -> 7
      6+8 -> 20     DSR+DCD - DTR       3 -> 20  (DCD - DTR)
       20 -> 6+8    DTR - DSR+DCD       7 -> 8   (DTR - DCD)
                                        2 -> n/c or pin 6 (see note below)

##### Notes:

- Shield ground is typically optional.
- TxD drives RxD.
- RTS drives CTS.
- DTR drives DSR and DCD.
- GND must always be connected straight through.
- In many cases on an RJ-45 connection, DSR is not connected to anything. It is very hard to short signals together on modular cables. However, if you are using a DEC machine, you may wish to find a way to also connect this signal to pin 20 (DTR) at the DB-25. DEC machines, unlike most other UNIX platforms, acknowledge the DSR signal.

#### No-handshaking Null-modem Connector

    (DTE)           (DTE)
    -----           -----
     SG) ----------- SG
     TxD ----------- RxD
     RxD ----------- TxD
     DCD --+     +-- DCD |
     DSR --+     +-- DSR |- modem control loopback
     DTR --+     +-- DTR |
     GND ----------- GND
     RTS --+     +-- CTS |
     CTS --+     +-- RTS |- hardware flow control loopback

    Example pin connections:
    ------------------------

    DB-25 -> DB-25           CD RJ-45 -> DB-25
    --------------           -----------------
        2 -> 3     TxD - RxD       5 -> 3
        3 -> 2     RxD - TxD       4 -> 2
        6+8+20    DSR+DCD+DTR      2, 3, and 7 not connected. (see note below)
        7 -> 7     GND - GND       6 -> 7
        4+5         RTS+CTS        1 and 8 not connected. (see note below)

##### Notes:

- The only lines that are actually connected from one device to the other are RxD, TxD, and GND.
- Only software (XON/XOFF) flow control can be used.
- CTS and RTS can be left open, but care must be taken to make sure one doesn't accidentally enable hardware flow control on either end.
- DCD and DSR don't have to be connected to DTR, but care must be taken to use a non-blocking node, or an application that opens in non-blocking mode. Otherwise, if a blocking node is used, and you have chosen not to locally connect these signals together, the application will hang forever waiting for DCD, which will never go true.
- On RJ-45 connectors, it is very difficult to locally connect pins together, so in the diagram above, the pins are simply not connected at all. Care must be taken to use a non-blocking device node when using this type of connector.

#### Possible Printer Null-modem Connector

Some terminals are designed to use DTR and CTS for hardware flow control instead of the more common RTS/CTS pairing. Some serial printers are also designed this way. In these cases, the following diagram can be used:

    (DTE)      (Terminal/Printer)
    -----      ------------------
     SG  ------------- SG
     TxD ------------- RxD
     RxD ------------- TxD
     RTS ------------- CTS
     CTS ------------- DTR
     GND ------------- GND
     DSR --+
     DCD --+
     DTR --+

    Example pin connections:
    ------------------------

    DB-25 -> DB-25              CD RJ-45 -> DB-25
    --------------              -----------------
         2 -> 3      TxD - RxD        5 -> 3
         3 -> 2      RxD - TxD        4 -> 2
         4 -> 5      RTS - CTS        1 -> 5
         5 -> 20     CTS - DTR        8 -> 20
         7 -> 7      GND - GND        6 -> 7
    6+8+20 -> n/c   DSR+DCD+DTR       2 -> not connected. +
                                      3 -> not connected. +-(see note below)
                                      7 -> not connected. +

##### Notes:

- The computer drives its own DCD and DSR with its DTR.
- The computer drives the terminals CTS with its RTS.
- The terminal drives the computer's CTS with its DTR.
- On RJ-45 connectors, it is very difficult to locally connect pins together, so in the previous diagram, the pins are simply not connected at all. Care to use a non-blocking device node when using this type of connector.