Function Code 04H; Function Code 05H - GE Multilin MM200 Communications Manual

CHAPTER 2: RS485 INTERFACE (MODBUS RTU)

Function Code 04H

Function Code 05H

MM200 MOTOR MANAGEMENT SYSTEM – COMMUNICATIONS GUIDE
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
BYTE COUNT
DATA 1 (see definition above)
DATA 2 (see definition above)
DATA 3 (see definition above)
CRC
Modbus Implementation: Read Input Registers
MM200 implementation: Read Actual Values
For the MM200 implementation of Modbus, this function code can be used to read any
actual values ("input registers"). Input registers are 16 bit (two byte) values transmitted high
order byte first. Thus all MM200 Actual Values are sent as two bytes. The maximum
number of registers that can be read in one transmission is 125.
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 2-2: MASTER/SLAVE PACKET FORMAT FOR FUNCTION CODE 04H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS
NUMBER OF ACTUAL VALUES
CRC
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
BYTE COUNT
DATA (see definition above)
CRC
Modbus Implementation: Force Single Coil
MM200 Implementation: Execute Operation
This function code allows the master to request a MM200 to perform specific command
operations.
BYTES EXAMPLE
1 11
1 03
1 06
2 02 2B
2 00 00
2 00 64
2 54 83
BYTES EXAMPLE
1 11
1 04
2 00 08
2 00 01
2 B2 98
BYTES EXAMPLE
1 11
1 04
1 02
2 00 00
2 78 F3
MODBUS FUNCTIONS
DESCRIPTION
message from slave
17
read registers
3 registers = 6 bytes
value in address
006B
value in address
006C
value in address
006D
CRC error code
DESCRIPTION
message for slave 17
read registers
data starting at 0008
1 register = 2 bytes
CRC error code
DESCRIPTION
message from slave
17
read registers
1 register = 2 bytes
value in address
0008
CRC error code
2-5