Function Code 03H; Function Code 04H - GE Multilin MM3 Motor Manager 3 Instruction Manual

SUPPORTED MODBUS FUNCTIONS
8.2.3 Function Code
03h
8.2.4 Function Code
04h
8–6
Modbus implementation: Read holding registers
MM3 Motor Manager 3 implementation: Read setpoints and actual values
For the MM3 Motor Manager 3 implementation of Modbus, this command can be used to
read any setpoints (holding registers) or actual values (input registers). Holding and input
registers are 16-bit (two-byte) values transmitted high order byte first. Thus all MM3 Motor
Manager 3 setpoints and actual values are sent as two bytes. The maximum number of
registers that can be read in one transmission is 125. This function code is identical to
function code 04.
The slave response to this function code is the slave address, function code, a count of the
number of 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, consider a request for slave 17 to respond with 3 registers starting at address
006B. For this example the register data in these addresses is as follows:
The master/slave packets have the following format:
Master transmission
Slave address
Function code
Data starting address
Number of setpoints
CRC
Slave response
Slave address
Function code
Byte count
Data word 1 (see definition above)
Data word 2 (see definition above)
Data word 3 (see definition above)
CRC (low, high)
Modbus implementation: Read input registers
MM3 Motor Manager 3 implementation: Read setpoints and actual values
For the MM3 Motor Manager 3 implementation of Modbus, this command can be used to
read any setpoints (holding registers) or actual values (input registers). Holding and input
registers are 16 bit (two byte) values transmitted high order byte first. Thus all MM3 Motor
Manager 3 setpoints and actual values are sent as two bytes. The maximum number of
registers that can be read in one transmission is 125. This function code is identical to
function code 03.
Address Data
006B 022B
006C 0000
006D 0064
Bytes Example
1 11
1 03
2 00 6B
2 00 03
2 76 87
Bytes Example
1 11
1 03
1 06
2 02 2B
2 00 00
2 00 64
2 54 83
MM3 MOTOR MANAGER 3 – INSTRUCTION MANUAL
CHAPTER 8: COMMUNICATIONS
Description
message for slave 17
read registers
data starting at 006Bh
3 registers = 6 bytes total
computed CRC error code
Description
message from slave 17
read registers
3 registers = 6 bytes
value in address 006Bh
value in address 006Ch
value in address 006Dh
computed CRC error code