For Modbus instructions not in the product manual, they can be generated in the following two ways:
① . dam debugging software generation
Ø when using dam debugging software to generate instructions, there is no need to connect and communicate with the equipment, just open any serial port. Take the generation of relay flash off mode command as an example, as shown in the following figure:
Ø generate and read analog input instruction:
Ø if the current computer has no serial port number, you can install virtual serial port software to virtual a serial port.
Click to download virtual serial port software
② Calculation and generation, MODBUS CRC verification generation tool
Ø when using the Modbus CRC verification generation tool, you need to understand the byte meaning of Modbus instruction (hexadecimal). An example of single channel read instruction is as follows:
Modbus example instruction | Device address | Function code | Start register address | Number of registers | CRC check code |
Do relay status | FE | 1 | 00 00 | 00 01 | E9 C5 |
Di switching value input | FE | 2 | 00 00 | 00 01 | AD C5 |
AI analog input | FE | 4 | 00 00 | 00 01 | 25 C5 |
Ø software generation instructions