MODBUS© Protocol is a messaging structure, widely used to establish master-slave
communication between intelligent devices. A MODBUS message sent from a master to a slave
contains the address of the slave, the 'command' (e.g. 'read register' or 'write register'), the
data, and a check sum (LRC or CRC).
Since Modbus protocol is just a messaging structure, it is independent of the underlying
physical layer. It is traditionally implemented using RS232, RS422, or RS485