Function Code 07: Read Device Status; Function Code 08: Loopback Test - GE 469 Instruction Manual

6 COMMUNICATIONS
Modbus Implementation: Read Exception Status
469 Implementation: Read Device Status
This is a 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 will have individual bits set to 1 or 0 depending on the status of the slave device.
469 General Status Byte:
Bit No. Description
B0 R1 Trip relay operated = 1
B1 R2 Auxiliary relay operated = 1
B2 R3 Auxiliary relay operated = 1
B3 R4 Alarm relay operated = 1
If status is neither stopped or running, the motor is starting.
MESSAGE FORMAT AND EXAMPLE:
Request status from slave 11.
MASTER TRANSMISSION:
SLAVE ADDRESS
FUNCTION CODE
CRC
SLAVE RESPONSE:
SLAVE ADDRESS
FUNCTION CODE
DEVICE STATUS
CRC
Modbus Implementation:
469 Implementation:
This function is used to test the integrity of the communication link. The 469 will echo the request.
MESSAGE FORMAT AND EXAMPLE:
Loopback test from slave 11.
MASTER TRANSMISSION:
SLAVE ADDRESS
FUNCTION CODE
DIAG CODE
DATA
CRC
SLAVE RESPONSE:
SLAVE ADDRESS
FUNCTION CODE
DIAG CODE
DATA
CRC
GE Multilin
Courtesy of NationalSwitchgear.com
Bit No.
B4
B5
B6
B7
BYTES EXAMPLE / DESCRIPTION
1 0B
1 07
2 47 42
BYTES EXAMPLE / DESCRIPTION
1 0B
1 07
1 59
2 C2 08
Loopback Test
Loopback Test
BYTES EXAMPLE / DESCRIPTION
1 0B
1 08
2 00 00
2 00 00
2 E0 A1
BYTES EXAMPLE / DESCRIPTION
1 0B
1 08
2 00 00
2 00 00
2 E0 A1
469 Motor Management Relay
6.2 MODBUS FUNCTIONS

6.2.6 FUNCTION CODE 07: READ DEVICE STATUS

Description
R5 Block start relay operated = 1
R6 Service relay operated = 1
Stopped = 1
Running = 1
message for slave 11
read device status
CRC calculated by the master
response message from slave 11
read device status
status = 01011001 in binary
CRC calculated by the slave

6.2.7 FUNCTION CODE 08: LOOPBACK TEST

message for slave 11
loopback test
must be 00 00
must be 00 00
CRC calculated by the master
response message from slave 11
loopback test
must be 00 00
must be 00 00
CRC calculated by the slave
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