Pull-Up And Pull-Down Resistors; Termination Resistor - ABB ControlMaster CM10 Communications Supplement

ControlMaster CM10, CM15, CM30 and CM50
Universal process controllers and indicators,

5.4 Pull-up and Pull-down Resistors

To prevent false triggering of slaves when the master (host computer) is inactive, pull-up and pull-down resistors must be fitted
to the RS422/485 interface in the host computer.
Resistors are normally connected to the interface by hard-wired links or switches – refer to the manufacturer's instructions

5.5 Termination Resistor

For long transmission lines, a 120 termination resistor must be fitted to the last slave in the chain – see Fig. 5.2.
Tx+
Tx–
Rx+
Rx–
COM
120 
Termination Resistor
Fig. 5.2 Connecting Multiple Slaves
16
1 1
/ , /
8
Last Slave
Standard
Connections
1
and / DIN
4 2
First Slave
Tx+
Tx–
Rx+
Rx–
COM
Standard
Connections
5 MODBUS Communications
Master
Rx+
Rx–
Tx+
Tx–
COM
Host
Computer
IM/CM/C–EN