gefran BDI50 Manuel D'utilisation page 161

4.4 LOOP BACK testing [08H]
The function code checks communication between MASTER and SLAVE, the Instruction
message is returned as a response message without being changed. Any values can be
used for test codes or data.
Instruction Message
3AH STX
30H
SLAVE
Address
31H
30H
Function Code
38H
30H
30H
Test Code
30H
30H
41H
35H DATA
33H
37H
31H
LRC CHECK
42H
0DH
END
0AH
Instruction Message
SLAVE Address
Function Code
High
Test Code
Low
High
DATA
Low
High
CRC-16
Low
Response Message (Normal)
3AH
30H
31H
30H
38H
30H
30H
30H
30H
41H
35H
33H
37H
31H
42H
0DH
0AH
Response Message (Normal)
01H SLAVE Address
08H Function Code
00H
Test Code
00H
A5H
DATA
37H
DAH
CRC-16
8DH
ASCII Mode
STX
SLAVE
Address
Function Code
Test Code
DATA
LRC CHECK
END
RTU Mode
01H
08H
High
00H
Low
00H
High
A5H
Low
37H
High
DAH
Low
8DH
App 3-9
Response(Fault)
3AH
30H
SLAVE
Address
31H
38H
Function Code
38H
32H
Error Code
30H
37H
LRC CHEC
35H
0DH
0AH
Response(Fault)
SLAVE Address
Function Code
Error Code
High
CRC-16
Low
STX
END
01H
88H
20H
47H
D8H