Rs422 And Rs485 Operating Modes - Siemens S7-1200 System Manual

12.3.5.2

RS422 and RS485 operating modes

Configuring the RS422
For RS422 mode, there are three operating modes depending on your network configuration.
Select one of these operating modes based on the devices in your network. The different
selections for Receive line initial state reference the cases shown below for more details.
● Full duplex (RS422) four wire mode (point-to-point connection): select this option when
● Full duplex (RS422) four wire mode (multipoint master): select this option for the master
● Full duplex (RS422) four wire mode (multipoint slave): Select this option for all the slave
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
there are two devices on your network. In the Receive line initial state:
– Select none when you supply the bias and termination (Case 3).
– Select forward bias to use internal bias and termination (Case 2).
– Select reverse bias to use internal bias and termination, and enable cable break
detection for both devices (Case 1).
device when you have a network with one master and multiple slaves. In the Receive line
initial state:
– Select none when you supply the bias and termination (Case 3).
– Select forward bias to use internal bias and termination (Case 2).
– Cable break detection is not possible in this mode.
devices when you have a network with one master and multiple slaves. In the Receive
line initial state:
– Select none when you supply the bias and termination (Case 3).
– Select forward bias to use internal bias and termination (Case 2).
– Select reverse bias to use internal bias and termination, and enable cable break
detection for the slaves (Case 1).
Communication processor and Modbus TCP
12.3 Point-to-point (PtP) communication
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