Function Code 07H (Read Device Status) - GE Multilin 850 Communications Manual

CHAPTER 11: MODBUS PROTOCOL

Function Code 07H (Read Device Status)

8 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
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
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
CRC (low, high)
Table 11-10: Slave Packet Format for Function Code 07H
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
DEVICE STATUS
(see following table)
CRC (low, high)
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
Bit mask
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
FUNCTION CODE 07H (READ DEVICE STATUS)
BYTES EXAMPLE
1 FE
1 07
2 00 12
BYTES EXAMPLE
1 FE
1 07
1 28
2 12 1E
Description
SP Group 3 Active
SP Group 2 Active
Pickup State
Breaker Connected
Breaker Closed
Breaker Tripped
Alarm
Trip
DESCRIPTION
message for slave 254
read device status
CRC error code
DESCRIPTION
message from slave 254
read device status
status = 00101000 (in binary)
CRC error code
11-7