There is nothing special about MODBUS, port and station of MACH3. The key is that the register address is 10. For example, the virtual port enabling address of Huichuan SV660P servo driver is H3 100, and the supported MODBUS commands are X03, X06 and X 10. Therefore, you should select "Hold Register" in MACH3. PS: If reading or writing a 32-bit register, enter 2 in the number. Reading and writing more than one register at a time is not recommended, but if reading and writing are necessary, the number must correspond to the number of 16 and 32 bits mentioned above. As for how to deal with it after reading MACH3, or how to deal with it after writing slave, it's up to you