Function Code 05H: Execute Operation - GE 750 Manual

CHAPTER 3: MODBUS FUNCTIONS

Function Code 05h: Execute Operation

750/760 FEEDER MANAGEMENT RELAY – COMMUNICATIONS GUIDE
Since some PLC implementations of Modbus only support one of function codes 03h and
04h, the 750/760 interpretation allows either function code to be used for reading one or
more consecutive data registers. The data starting address will determine the type of data
being read. Function Codes 03h and 04h are therefore identical.
The following table shows the format of the master and slave packets. The example shows
a master device requesting 3 register values starting at address 200h from slave device 11;
the slave device responds with the values 555, 0, and 100 from registers 200h, 201h, and
202h respectively.
Master Transmission
Slave Address
Function Code
Data Starting Address
Number of Registers
CRC (low, high)
Slave Response
Slave Address
Function Code
Byte Count
Data #1 (high, low)
Data #2 (high, low)
Data #3 (high, low)
CRC (low, high)
This function code allows the master to perform various operations in the 750/760.
Operations are shown in the Summary of Operation Codes for Function 05h table.
The following table shows the format of the master and slave packets. The example shows
a master device requesting the slave device 11 to perform a reset. The 'high' and 'low'
Code Value bytes always have the values FFh and 00h, respectively and are a remnant of
the original Modbus definition of this function code.
Master Transmission
Slave Address
Function Code
Operation Code
Code Value
CRC (low, high)
Slave Response
Slave Address
Function Code
FUNCTION CODE 05H: EXECUTE OPERATION
Bytes Example
1 11 message for slave 11
1 03 read register values
2 02 00 data starting at 0200h
2 00 03 3 registers = 6 bytes total
2 06 E3 computed CRC error code
Bytes Example
1 11 message from slave 11
1 03 read register values
1 06 3 values = 6 bytes total
2 02 2B value in address 0200h
2 00 00 value in address 0201h
2 00 64 value in address 0202h
2 C8 BA computed CRC error code
Bytes Example
1 11 message for slave 11
1 05 execute operation
2 00 01 remote reset
2 FF 00 perform operation
2 DF 6A computed CRC error code
Bytes Example
1 11 message from slave 11
1 05 execute operation
Description
Description
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