6MM300 MOTOR MANAGEMENT SYSTEM – COMMUNICATIONS GUIDE
RS485 INTERFACE (MODBUS RTU) COMMUNICATIONS GUIDE
The slave response to this function code is the slave address, function code, a count of the
data bytes to follow, the data itself and the CRC. Each data item is sent as a two byte
number with the high order byte sent first.
For example, request slave 17 to respond with 1 register starting at address 0008. For this
example the value in this register (0008) is 0000.
Table 2: Master/slave packet format for function code 04H
Function Code 05H
Modbus Implementation: Force Single Coil
MM300 Implementation: Execute Operation
This function code allows the master to request a MM300 to perform specific command
operations.
For example, to request slave 17 to execute operation code 1 (reset), we have the following
master/slave packet format:
Table 3: Master/slave packet format for function code 05H
MASTER TRANSMISSION BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message for slave
17
FUNCTION CODE 1 04 read registers
DATA STARTING ADDRESS 2 00 08 data starting at
0008
NUMBER OF ACTUAL VALUES 2 00 01 1 register = 2 bytes
CRC 2 B2 98 CRC error code
SLAVE RESPONSE BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message from
slave 17
FUNCTION CODE 1 04 read registers
BYTE COUNT 1 02 1 register = 2 bytes
DATA (see definition above) 2 00 00 value in address
0008
CRC 2 78 F3 CRC error code
MASTER TRANSMISSION BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message for slave
17
FUNCTION CODE 1 05 execute operation
OPERATION CODE 2 00 01 operation code 1
CODE VALUE 2 FF 00 perform function
CRC 2 DF 6A CRC error code
SLAVE RESPONSE BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 11 message from
slave 17
FUNCTION CODE 1 05 execute operation
OPERATION CODE 2 00 01 operation code 1
CODE VALUE 2 FF 00 perform function
CRC 2 DF 6A CRC error code