Communications D - 5 Message FormatIn Modbus communication, the master sends commands to the slave, and the slave responds. The message format isconfigured for both sending and receiving as shown below. The length of the data packet is controlled by the command(function) contents.Fig D.4 Message FormatThe space between messages must support the following:Fig D.5 Message SpacingSlave AddressSet the Drive address from 0 to 20 Hex. If 0 is selected, commands from the master will be broadcast (i.e., the Drive will notreturn a response message).Function CodeThe function code specifies command type. There are four function codes, as shown below.Slave addressFunction codeDataError checkTable D.3 Modbus Function CodesFunction Code(Hexadecimal) FunctionCommand Message Response MessageMin.(Bytes)Max.(Bytes)Min.*(Bytes)Max.(Bytes)03H Reading/Holding Register Contents 8 8 7 2106H Write In Single Holding Register 8 8 8 808H Loopback Test 8 8 8 810H Write In Several Holding Registers 11 41 8 8* Minimum bytes for a normal Response Message (error response message is always 5 bytes).PLC to DriveDrive to PLCPLC to DriveCommand message Response message Command messageTime (Seconds)24 bits long 5ms min.H5-06setting24 bits long
