User Manual of EM760 High-Performance Inverter Fig. 10-2 Schematic Diagram of Message Frame in RTU Mode The RTU message includes the address code, PDU (Protocol Data Unit) and CRC [3] check. The PDU includes the function code and data part (mainly including the register address, number of registers, register content and the like; the detailed definitions of function codes are different, as shown in 11.3.3). [3]: The low byte of CRC check is infront of the high byte 10.3.2 Address code 10.3.3 Function code The classification of MODBUS function codes is shown in the figure below. Fig.
10-3 Classification of MODBUS function codes As shown in the table below, EM760 series products mainly involve common function codes . For example,0x03 is to read multiple registers or status words, 0x06 is to write a single register or command, 0x10 is to write multiple registers or commands, and 0x08 is for diagnosis. 254 Address Range Purpose 1~247 Slave 0 Broadcast