Communication from Quantum using modbusplus port


Thread Starter


Q. Is it possible to communicate Quantum 434 PLC using its modbusplus port with a Yokogawa DCS having RS 485 protocol without using any gateway?

On physical verification i have seen modbusplus cable coming from Quantum PLC has three wire Tx, Rx, Screen. Whereas the DCS using RS 485 has four wires.
NO! The Quantum 434 processor Modbus ports are RS232 and the Yokagawa ports are RS485. Two different electrical interfaces. They cannot be directly wired to each other. Even if both "speak" Modbus protocol, you MUST USE a RS232 to RS485 convertor.
Modbus Plus is a proprietary protocol running on a modified RS485 network, it is not simply modbus protocol over a RS485 network.