Manual Number: 00650-146-1
Page 10
PCI-COM485/8 Manual
Chapter 3: Option Selection
To help you locate the jumpers described in this section, refer to the OPTION SELECTION MAP
at the end of this section. Operation of the serial communications section is determined by jumper
installation as described in the following paragraphs.
Terminations
A transmission line should be terminated
at the receiving end in its characteristic
impedance. Installing a jumper at the
locations labeled LDxO applies a 120
load across the transmit/receive
input/output for RS-485 operation.
Simplified Termination Schematic
In RS-485 operations where there are multiple terminals, only the RS-485 ports at each end of the
network should have terminating impedance as described above. To so terminate the COM A port,
place a jumper at the location labeled LDAO. To terminate the COM B, COM C, COM D, COM E,
COM F and COM H ports, place jumpers at locations labeled LDBO, LDCO, LDDO, LDEO,
LDFO and LDHO respectively.
Also, for RS-485 operation, there must be a bias on the RX+ and RX- lines.
If the COM485/8 card
is not to provide that bias, contact the factory technical support.
Data Cable Wiring
Signal
Connector Pin
Ain-
Pin 1
Aout+
Pin 2
Aout-
Pin 3
100 Ohm to Ground
Pin 5
Ain+
Pin 9
