Manual 104i-COM-8SM
18
Port to Port Cable Wiring
The following connections are used to communicate between two ports (usually on different
devices), depending on the communication mode:
Note that the user cable MUST include a ground to ground connection for RS-232,
RS-422
and
RS-485 as high common mode between external devices will burn out
the transceiver
IC’s.
Mode
Cable Pins
Port 1
to
Port 2
RS-232
RX
to
TX
TX
to
RX
Ground
to
Ground
RS-422 Full-Duplex
1
RX+
to
TX+
RX-
to
TX-
TX+
to
RX+
TX-
to
RX-
Ground
to
Ground
RS-422 Simplex Receive Only
RX+
to
TX+
RX-
to
TX-
Ground
to
Ground
RS-422 Simplex Transmit Only
TX+
to
RX+
TX-
to
RX-
Ground
to
Ground
RS-485 Half-Duplex
TX+/RX+
to
TX+/RX+
TX-/RX-
to
TX-/RX-
Ground
to
Ground
1
RS-485 4-Wire
(not a TIA/EIA standard)
Port 1 designates the Master,
should be an RS-422 (TX not shared)
Port 2 designates the Slaves,
must be an RS-485 (TX shared)
Table 6-6:
Port to Port Cable Wiring
