Communication processor and Modbus TCP
13.3 Point-to-point (PtP) communication
S7-1200 Programmable controller
1142 System Manual, V4.2, 09/2016, A5E02486680-AK
Case 3: RS422: No cable break detection, no bias
● Mode of operation: RS422
● Receive line initial state: no bias
● Cable break: No cable break detection (transmitter enabled only while transmitting)
Bias and termination are added by the user at the end nodes of the network.
For RS485 mode, there is only one operating mode. The different selections for Receive line
initial state reference the cases shown below for more details.
● Half duplex (RS485) two wire mode. In the Receive line initial state:
– Select none when you supply the bias and termination (Case 5).
– Select forward bias to use internal bias and termination (Case 4).
Case 4: RS485: Forward bias
● Mode of operation: RS485
● Receive line initial state: Forward bias (biased with R(B) > R(A) > 0 V)
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