Communication processor and Modbus TCP
12.2 Biasing and terminating an RS485 network connector
S7-1200 Programmable controller
670 System Manual, 03/2014, A5E02486680-AG
Biasing and terminating an RS485 network connector
Siemens provides an RS485 network connector (Page 991) that you can use to easily
connect multiple devices to an RS485 network. The connector has two sets of terminals that
allow you to attach the incoming and outgoing network cables. The connector also includes
switches for selectively biasing and terminating the network.
Note
You terminate and bias only the two ends of the RS485 network. The devices in between the
two end devices are
not terminated or biased. Bare cable shielding: Approximately 12 mm
(1/2 in) must contact the metal guides of all locations.
Switch position = On: Terminated and biased
Switch position = Off: No termination or bias
Switch position = On: Terminated and biased
Table 12- 1 Termination and bias for the RS485 connector
Terminating device (bias ON)
Non-terminating device (bias OFF)
Pin number
Network connector
The CB 1241 provides internal resistors for terminating and biasing the network. To
terminate and bias the connection, connect TRA to TA and connect TRB to TB to include the
internal resistors to the circuit. CB 1241 does not have a 9-pin connector. The following table
shows the connections to a 9-pin connector on the communications partner.
To Next Page
Loading...
