Appendix A Communication in RTU mode 1. Communication data structure 2. Communication address The valid communication address is 0 ～ 254. The communication address 0 indicates to broadcast the message to all slaves and the slaves which have received the broadcast message do not make any response. If the communication address is not 0, slaves will reply to master as normal. For example, to communication with the slave with the communication address of 16, the address of the slave is set as 0x10 since decimal 16 is equal to hexadecimal 10. 3. Function code and data The data format is determined by function codes.
For example, to read the data of two continuous addresses with 0x1000 as start address in DVP10MC11T, the address of DVP10MC11T is 1, 0x1000 is the Modbus address of D0 in DVP10MC11T PLC. The data in the communication cable and the explanation on them are shown below: PC→DVP10MC11T: “01 03 10 00 00 02 C0 CB” DVP10MC11T→PC: “01 03 04 01 00 02 00 FA AF” DVP-MC operating manual A-9 ASCII code corresponding to field Field name Field character character Data number (Counted by words): 2 “0” 30 “0” 30 “0” 30 “2” 32 LRC check code: 0xEA “E” 45 “A” 41 End character 1: LF CR 0D End character 0: CR LF 0A Start No input data for more than 10ms Communication address Slave address:
8-bit binary address Function code Function code: 8-bit binary address Data（n-1） Data content n × 8 bit binary data, n ……. Data 0 Low byte of CRC check CRC check sum CRC check sum is composed of two 8-bit binary data High byte of CRC check End No input data for more than 10ms