Autonomous system (without networking) (a)

There is only a process station with local HMI connected to the I/O bus at the most simple topologies.

PLC and I/O modules over a RS485 bus


mark220          PLC –a Merbon process station
R…                  I/O modules – according to the plant I/O mix

The bus is connected directly at the RS485 interface (terminals K+, K-) of the process station. There is nothing else connected to the PLC apart from 24 V power supply. The PLC is operated using LCD display and a 6-button keyboard. The Ethernet interface is only used for commissioning and service.