
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
Содержание 850
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