Chapter 3: Option Selection
Operation of the serial communications section is determined by jumper installation as
described in the following paragraphs. Locations of the jumpers are shown in Figure 3-1,
Option Selection at the end of this section of the manual.
422/485
Jumpers must be installed in these blocks for each COM port. The function of the 422 and 485
jumpers is to configure the port for RS-422 or RS-485 mode communications. Either an RS-422
or RS-485 jumper must be used for each channel.
Terminations and Bias
A transmission line should be terminated at the receiving end in its characteristic impedance.
Installing a jumper at the location labeled LDO applies a 120
Ω
load across the output for RS-
422 mode and across the transmit/receive input/output for RS-485 operation.
Installing a jumper at the location labeled LDI applies a 120
Ω
load across the input for RS-422
operation.
The card provides biasing for the RS-485 mode.
CLK X1 and CLK X4
Placement of this jumper 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 numbers are joined together with a "&" the two pins are jumpered together.
CABLE
MODE
JUMPERS
CARD1
CARD2
Simplex
2-wire
Receive Only
422
Rx+ 9
2
Rx-
1
3
Simplex
2-wire
Transmit Only 422
Tx+ 2
9
Tx-
3
1
Half Duplex
2-wire
485
TRx+ 2
2
TRx-
3
3
Full
Duplex 4-wire
422
Tx+
2 9
Tx-
3
1
Rx+
9
2
Rx-
1
3
