CPN model of the MODBUS protocol

Coloured Petri Nets (CPN) has been developed as a modeling language mainly for the parallel processes and communication protocols. CPN were used for modeling of various protocols, i.e. TCP/IP or CAN. In this paper it is presented CPN model of the MODBUS over serial line protocol, which is defined on the 2nd layer of ISO/OSI reference model. The model of MODBUS protocol (Figure 1) consists of model of master device, several slave devices and communication network. Each of connected slave devices has its own configuration stored in place confl (or conf2). MODBUS over serial line protocol defines master/slave communication principle.