GE D90 Plus - Page 10

6D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – COMMUNICATIONS GUIDE
MODBUS FUNCTION CODES CHAPTER 2: MODBUS COMMUNICATION
The following tables show the format of the master and slave packets. The example shows
a master device requesting three register values starting at address 4050h from slave
device 11h (17 decimal); the slave device responds with the values 40, 300, and 0 from
registers 4050h, 4051h, and 4052h, respectively.
Table 3: Master transmission packet example, function code 04h
Table 4: Slave response packet example, function code 04h
Execute command
The execute command function allows the master to perform operations in the relay. The
following table outlines the operations available.
Table 5: Summary of operation codes for function 05h
The following tables illustrate the format of the master and slave packets for function code
05h. The example shows a master device requesting the slave device 11h (17 decimal) to
perform a reset. The high and low code value bytes always have the values “FF” and “00”
respectively and are a remnant of the original Modbus definition of this function code.
Packet format Example (hex)
Slave address 11
Function code 04
Data starting address - high order byte 40
Data starting address - low order byte 50
Number of registers - high order byte 00
Number of registers - low order byte 03
CRC - low order byte A7
CRC - high order byte 4A
Packet format Example (hex)
Slave address 11
Function code 04
Byte count 06
Data byte 1 - high order byte 00
Data byte 1 - low order byte 28
Data byte 2 - high order byte 01
Data byte 2 - low order byte 2C
Data byte 3 - high order byte 00
Data byte 3 - low order byte 00
CRC - low order byte 0D
CRC - high order byte 60
Operation code Definition Description
0000h NO OPERATION Does not do anything
0001h RESET Performs the same function as the Reset command
0005h CLEAR EVENT RECORDS Performs the same function as the Clear Event
Records
command
0006h CLEAR OSCILLOGRAPHY Clears all oscillography records
1000h to 103Fh VIRTUAL IN 1 to 64 ON/OFF Sets the states of virtual inputs 1 to 64 either “ON”
or “OFF”