GE 489 Communications Manual page 11

CG.2.5 Function Code 07: Read Device Status
489 GENERATOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE
Message Format and Example:
Request slave 11 to store the value 01F4 in Setpoint address 1180. After the transmission
in this example is complete, Setpoints address 1180 will contain the value 01F4.
Master Transmission
Slave Address
Function Code
Data Starting Address
Data
CRC (low, high)
Slave Response
Slave Address
Function Code
Data Starting Address
Data
CRC (low, high)
Modbus Implementation: Read Exception Status
489 Implementation: Read Device Status
This function reads the selected device status. A short message length allows for rapid
reading of status. The returned status byte has individual bits set to 1 or 0 depending on
the slave device status. The 489 general status byte is shown below:
Bit Description
B0 1 TRIP relay operated = 1
B1 2 AUXILIARY relay operated = 1
B2 3 AUXILIARY relay operated = 1
B3 4 AUXILIARY relay operated = 1
Note that if the generator status is neither Offline nor Online, the generator status is
Tripped.
Message Format and Example:
Request status from slave 11.
Master Transmission
Slave Address
Function Code
CRC (low, high)
Slave Response
Slave Address
Function Code
Device Status
Bytes Example
1 0B message for slave 11
1 06 store single setpoint
2 11 80 setpoint address 1180h
2 01 F4 data for address 1180h
2 8D A3 computed CRC error code
Bytes Example
1 0B message from slave 11
1 06 store single setpoint
2 11 80 setpoint address 1180h
2 01 F4 data for address 1180h
2 8D A3 computed CRC error code
Bit
B4 5 ALARM relay operated = 1
B5 6 SERVICE relay operated = 1
B6 Offline = 1
B7 Online = 1
Bytes Example
1 0B message for slave 11
1 07 read device status
2 47 42 computed CRC error code
Bytes Example
1 0B message from slave 11
1 07 read device status
1 59 status = 01011001b
Description
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Description
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Description
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