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Modbus Functions
489
Communications Guide
http://www.GEindustrial.com/multilin
7
GE Multilin
Function Code 16: Store
Multiple Setpoints
Modbus Implementation: Preset Multiple Registers
489 Implementation: Store Multiple Setpoints
This function code allows multiple Setpoints to be stored into the 489 memory.
Modbus “registers” are 16-bit (two byte) values transmitted high order byte first.
Thus all 489 setpoints are sent as two bytes. The maximum number of Setpoints
that can be stored in one transmission is dependent on the slave device. Modbus
allows up to a maximum of 60 holding registers to be stored. The 489 response to
this function code is to echo the slave address, function code, starting address, the
number of Setpoints stored, and the CRC.
Message Format and Example:
Request slave 11 to store the value 01F4 to Setpoint address 1180 and the value
0001 to setpoint address 1181. After the transmission in this example is complete,
489 slave 11 will have the following setpoints information stored:
Address Data
1180 01F4
1181 0001
Master Transmission Bytes Example Description
Slave Address 1 0B message for slave 11
Function Code 1 10 store setpoints
Data Starting Address 2 11 80 data starting at 1180h
Number of Setpoints 2 00 02 2 setpoints = 4 bytes total
Byte Count 1 04 2 registers = 4 bytes
Data 1 2 01 F4 data for address 1180h
Data 2 2 00 01 data for address 1181h
CRC (low, high) 2 9B 89 computed CRC error code
Slave Response Bytes Example Description
Slave Address 1 0B message from slave 11
Function Code 1 10 store multiple setpoints
Data Starting Address 2 11 80 data starting at 1180h
Number of Setpoints 2 00 02 2 setpoints (4 bytes total)
CRC (low, high) 2 45 B6 computed CRC error code