Understanding the differences between Modbus and Modbus Plus are very important. Modbus is based on the RS232C serial standard communications that define the cabling, connector pinouts, signal levels, parity checking, and transmission baud rates. It’s a master slave protocol that uses the Modicon controllers through a common language.
Modbus Plus, is a network protocol that uses high speeds between the networks of peer connections. Upon the receipt of the token frame, Modbus Plus nodes on the access of the network. When the node hold a token, it can start transactions with several devices on the same network.