Terminations and Bias
A transmission line should be terminated at the receiving end in its characteristic impedance.
Installing a jumper at the location labeled TERM applies a 120
Ω
load across the input for RS422
mode and across the transmit/receive input/output for RS485 operation.
In RS485 operations, where there are multiple terminals, only the RS485 ports at each end of the
network should have terminating resistors as described above. Also, for RS485 operation, there
must be a bias on the RX+ and RX- lines. If the card is to provide that bias, install jumpers at the
locations labeled BIAS.
CLK X1 and CLK X4
Placement of these jumpers controls baud rate. CLK X1 permits baud rates up to 115.2K Baud
and CLK X4 permits baud rates up to 460.8K Baud.
Data Cable Wiring
When two pin numbers are joined together with a "&", those pins are wired together in the
external cable.
Cable
Mode
Jumpers
Signal
Card 1
Card 2
DCD 1
7&8
RX 2
3
TX 3
2
DTR 4
6
Ground 5
5
DSR 6
4
RTS 7
1
CTS 8
1
RS232
232 (x5)
RI 9
open
RS422/485
Rx+ 9
2
Simplex
(2-wire Receive
Only)
422 (x5)
Rx- 1
3
Tx+ 2
9
Simplex
(2-wire Transmit
Only)
422 (x5)
Tx- 3
1
Rx- & Tx-
1 & 3
1 & 3
Half-Duplex
(2-Wire no echo*)
422 (x5) AUTO or RTS
Tx+ & Rx+
2 & 9
2 & 9
1 & 3
1 & 3
Half-Duplex
(2-Wire with echo)
422 (x5) ECHO, AUTO or RTS
2 & 9
2 & 9
Tx+ 2
9
Tx- 3
1
Rx+ 9
2
Full-Duplex
(4-Wire)
422 (x5)
Rx- 1
3
* Preferred RS-485 mode.
Manual PCI-COM-2S
12