Loopback Test - Function Code 08 - ABB C250 User Manual

5.5 Loopback Test – Function Code 08
5.5.1 Loopback Test Query
The Loopback Test Query tests the MODBUS system and does not affect the
operation of the slave. Variations in the response may indicate faults in the MODBUS
system. The information field contains two bytes for the designation of the diagnostic
code followed by two bytes to designate the action to be taken.
Example
Address Function
01 08
*These are considered to be the information fields for the diagnostic mode.
5.5.2 Loopback Test Response
The Loopback Test Response always echoes the query, only diagnostic code 0
(bytes 3 and 4) can be used.
Example
Address Function
01 08
Data Data
Diagnostic Diagnostic
Code High Code Low
00 00
Data Data
Diagnostic Diagnostic
Code High Code Low
00 00
5 MODBUS Functions...
Error
Data* Data* Check
Field
A5 37
Error
Data Data Check
Field
A5 37
(CRC-16)
DA 8D
(CRC-16)
DA 8D
13