Connector Pin Assignments A
-3
Sub-network Interface
General Information
The sub-network interface provides for RS232, RS422 and RS485 communications. Depending on the
configuration specified in the ABC Config Tool, different signals are activated in the sub-network con-
nector.
Bias Resistors (RS485 Only)
When idle, RS485 enters an indeterminate state, which may cause the serial receivers to pick up noise
from the serial lines and interpret this as data. To prevent this, the serial lines should be forced into a
known state using pull-up and pull-down resistors, commonly known as bias resistors.
The bias resistors forms a voltage divider, forcing the voltage between the differential pair to be higher
then the threshold for the serial receivers, typically >200mV.
Note that bias resistors shall only be installed on one node; installing bias resistors on several nodes may
compromise the signal quality on the network and cause transmission problems.
Termination (RS485 & RS422 Only)
To avoid reflections on the serial lines, it is important to properly terminate the sub-network by placing
termination resistors between the serial receivers near the end nodes.
The resistor value should ideally match the characteristic impedance of the cable, typically 100... 120R.
Connector Pinout (DB9F)
Pin
Description
RS232
RS422
RS485
RS485
1
+5V Output(100mA max)
3
3
3
2
RS232 Rx
3
3
RS232 Tx
3
4
(reserved)
5
Signal Ground
a
a. Connecting this signal directly Protective Earth (PE) of other nodes may, in case of grounding loops etc., cause
damage to the on-board serial transceivers. It is therefore generally recommended to connect it only to Signal
Ground (if available) of other nodes.
3
3
3
6
RS422 Rx +
3
7
RS422 Rx -
3
8
RS485 + /RS422 Tx+
3
3
9
RS485 - /RS422 Tx-
3
3
(housing)
Cable Shield
3
3
3
IHPDOH
