RS422I-PA Manual
Page 3-2
Manual 00650-519-1
Terminations and Bias
A transmission line should be terminated at the receiving end in its characteristic impedance.
Installing a jumper at the location labeled TERMOUT applies a 120
S
load in series with a 0.1
:
F
capacitor across the output (if desired) for RS422 mode and across the transmit/receive
input/output for RS485 operation. A jumper at the TERMIN location applies a load on RS422
inputs.
Two-Wire Connection
Four-Wire Connection
Figure 3-1:
Simplified Schematic - Two-Wire and Four-Wire Connection
Full or Half-Duplex
Full-Duplex allows simultaneous bi-directional communications. Half-Duplex allows bi-directional
transmit and receiver communication but only one at a time, and is required for RS485
communications. Proper selection depends on the wire connections used to connect the two serial
ports. The following table shows how two serial communication cards would be interconnected for
the various modes. Tx designates the transmit wires and Rx designates the receive wires.
