CHAPTER 11: MODBUS PROTOCOL FUNCTION CODE 07H (READ DEVICE STATUS)
8 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE 11-7
Function Code 07H (Read Device Status)
Modbus Implementation: Read Exception Status
8 Series relay Implementation: Read Device Status
The function used to quickly read the status of a selected device. A short message length
allows for rapid reading of status. The status byte returned has individual bits set to 1 or 0
depending on the status of the slave device. For this example, consider the following
8
Series relay general status byte:
Table 11-9: Master Packet Format for Function Code 07H
Table 11-10: Slave Packet Format for Function Code 07H
ASE 2000 V2 Example
--> 00 00 00 00 00 02 FE 07
--> 00 00 00 00 00 03 FE 07 28
Function code 07H includes the following bit masks:
Table 11-11: Device Table Status
MASTER TRANSMISSION BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 FE message for slave 254
FUNCTION CODE 1 07 read device status
CRC (low, high) 2 00 12 CRC error code
SLAVE RESPONSE BYTES EXAMPLE DESCRIPTION
SLAVE ADDRESS 1 FE message from slave 254
FUNCTION CODE 1 07 read device status
DEVICE STATUS
(see following table)
1 28 status = 00101000 (in binary)
CRC (low, high) 2 12 1E CRC error code
Bit mask Description
Bit 0 SP Group 3 Active
Bit 1 SP Group 2 Active
Bit 2 Pickup State
Bit 3 Breaker Connected
Bit 4 Breaker Closed
Bit 5 Breaker Tripped
Bit 6 Alarm
Bit 7 Trip
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