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6 489 GENERATOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE

CG.2.3 Function Code 05: Execute Operation

Modbus Implementation: Force Single Coil

489 Implementation: Execute Operation

This function code allows the master to request specific 489 command operations. The

command numbers listed in the Commands area of the memory map correspond to

operation code for function code 05. The operation commands can also be initiated by

writing to the Commands area of the memory map using function code 16. Refer to

Section CG.2.7 Function Code 16: Store Multiple Setpoints on page –8 for complete details.

Supported Operations:Reset 489 (operation code 1); Generator Start (operation code 2);

Generator Stop (operation code 3); Waveform Trigger (operation code 4)

Message Format and Example:

Reset 489 (operation code 1).

CG.2.4 Function Code 06: Store Single Setpoint

Modbus Implementation: Preset Single Register

489 Implementation: Store Single Setpoint

This command allows the master to store a single setpoint into the 489 memory. The slave

response to this function code is to echo the entire master transmission.

CRC (low, high) 2 D5 17 computed CRC error code

Slave Response Bytes Example Description

Slave Address 1 0B message from slave 11

Function Code 1 03 read register values

Byte Count 1 04 2 registers = 4 bytes total

Data #1 (high, low) 2 00 64 value in address 0235h

Data #2 (high, low) 2 00 0A value in address 0236h

CRC (low, high) 2 EB 91 computed CRC error code

Master Transmission Bytes Example Description

Slave Address 1 0B message for slave 11

Function Code 1 05 execute operation

Operation Code 2 00 01 reset command (op code 1)

Code Value 2 FF 00 perform function

CRC (low, high) 2 DD 50 computed CRC error code