
CHAPTER 9: MODBUS FUNCTIONS
FUNCTION CODE 08H
350 FEEDER PROTECTION SYSTEM – COMMUNICATIONS GUIDE
9–5
Table 9-6: MASTER/SLAVE PACKET FORMAT FOR FUNCTION CODE 07H
Function Code 08H
Modbus Implementation: Loopback
Test 350 Implementation: Loopback Test
This function is used to test the integrity of the communication link. The 350 will echo the
request.
For example, consider a loopback test from slave 17:
Table 9-7: MASTER/SLAVE PACKET FORMAT FOR FUNCTION CODE 08H
5
52b Contact
6
Maintenance
7
Relay in Service
MASTER TRANSMISSION
BYTES
EXAMPLE
DESCRIPTION
SLAVE ADDRESS
1
11
message for slave 17
FUNCTION CODE
1
07
read device status
CRC
2
4C 22
CRC error code
SLAVE RESPONSE
BYTES
EXAMPLE
DESCRIPTION
SLAVE ADDRESS
1
11
message from slave
17
FUNCTION CODE
1
07
read device status
DEVICE STATUS (see definition
above)
1
2C
status = 00101100
(in binary)
CRC
2
22 28
CRC error code
Bit
Function
MASTER TRANSMISSION
BYTES
EXAMPLE
DESCRIPTION
SLAVE ADDRESS
1
11
message for slave 17
FUNCTION CODE
1
08
loopback test
DIAG CODE
2
00 00
must be 00 00
DATA
2
00 00
must be 00 00
CRC
2
E0 0B
CRC error code
SLAVE RESPONSE
BYTES
EXAMPLE
DESCRIPTION
SLAVE ADDRESS
1
11
message from slave
17
FUNCTION CODE
1
08
loopback test
DIAG CODE
2
00 00
must be 00 00
DATA
2
00 00
must be 00 00
CRC
2
E0 0B
CRC error code
Содержание ML Series 350
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