GE 850 Instruction Manual page 146

DEVICE
4–32
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
850 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
850 general status byte:
Table 4-13: Master Packet Format for Function Code 07H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
CRC
Table 4-14: Slave Packet Format for Function Code 07H
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
DEVICE STATUS
(see following table)
CRC
Function code 07H includes the following bit masks:
Table 4-15: Device Table Status
Bit mask
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
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
BYTES EXAMPLE
1 11
1 07
2 4C 22
BYTES EXAMPLE
1 11
1 07
1 2C
2 22 28
Description
SP Group 3 Active
SP Group 2 Active
Pickup State
Breaker Connected
Breaker Closed
Breaker Tripped
Alarm
Trip
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
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
DESCRIPTION
message for slave 17
read device status
CRC error code
DESCRIPTION
message from slave 17
read device status
status = 00101100 (in binary)
CRC error code