Operating instructions

Mounting and connecting
4.3 Connecting the HMI device
MP 377, MP 377 PRO (WinCC flexible)
70 Operating Instructions, 10/2008, 6AV6691-1DR01-0AB0
Configuring an RS-422/RS-485 port
A DIP switch S1 for the configuration of the RS-422/RS-485 port is located on the rear of
the HMI device.
In the factory state, the DIP switch is set for communication with the SIMATIC S7 PLC
via RS 485.
Note
Note the diagrams of DIP switch settings on the rear panel of the HMI device.
The following table shows the DIP switch settings. The send and receive direction is toggled
internally using the RTS signal.
Communication Switch setting Meaning

21
No RTS on connector,
• During data transfer between the PLC and HMI device
• During data transfer between the HMI device and PC
(delivery condition)

21
RTS on pin 4, same as PLC,
for example for commissioning
RS 485

21
RTS on pin 9, same as programming device,
for example for commissioning
RS 422

21
RS-422 port is active.