GE 845 Instruction Manual page 137

CHAPTER 4: SETPOINTS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
845 Implementation: Execute Operation
The function code allows the master to request a 845 to perform specific command
operations.
For example, to request slave 17 to execute operation code 1 (reset), we have the following
master/slave packet format:
Table 4-9: Master Packet Format for Function Code 05H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
OPERATION CODE
CODE VALUE
CRC
Table 4-10: Slave Packet Format for Function Code 05H
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
OPERATION CODE
CODE VALUE
CRC
Function Code 06H
Modbus Implementation: Preset Single Register
845 Implementation: Store Single Setpoint
The command allows the master to store a single setpoint into the memory of a 845 relay.
The slave response to this function code is to echo the entire master transmission.
For example, request slave 17 to store the value 2 in setpoint address 04 5C. After the
transmission in this example is complete, setpoints address 04 5C contains the value 0002.
The master/slave packet format is shown next.
Table 4-11: Master Packet Format for Function Code 06H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS
DATA
CRC
Table 4-12: Slave Packet Format for Function Code 06H
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS
DATA
CRC
Function Code 07H
Modbus Implementation: Read Exception Status
845 Implementation: Read Device Status
BYTES EXAMPLE
1 11
1 05
2 00 01
2 FF 00
2 DF 6A
BYTES EXAMPLE
1 11
1 05
2 00 01
2 FF 00
2 DF 6A
BYTES EXAMPLE
1 11
1 06
2 04 5C
2 00 02
2 CB B9
BYTES EXAMPLE
1 11
1 06
2 04 5C
2 00 02
2 CB B9
DESCRIPTION
message for slave 17
execute operation
operation code 1
perform function
CRC error code
DESCRIPTION
message from slave 17
execute operation
operation code 1
perform function
CRC error code
DESCRIPTION
message for slave 17
store single setpoint
setpoint address 04 5C
data for setpoint address 04 5C
CRC error code
DESCRIPTION
message from slave 17
store single setpoint
setpoint address 04 5C
data for setpoint address 04 5C
CRC error code
DEVICE
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