7300CV MODBUS COMMUNICATION PROTOCOL
File No. :PC-CV-08
Version : 1.A
Page :
27/34
6.5.3 Loop back testing [08H]
The function code is check communication between MASTER and SLAVE, the Instruction message is
returned as a response message without being change, Any values can be used for test codes or data
ASCII Mode
Instruction Message Response Message (Normal) Response Message (Fault)
3AH
STX
3AH
STX
3AH
STX
30H
30H
30H
31H
SLAVE
Address
31H
SLAVE
Address
31H
SLAVE
Address
30H
30H
38H
38H
Function
Code
38H
Function
Code
38H
Function
Code
30H
30H
32H
30H
30H
30H
Error Code
30H
30H
?
30H
Test Codes
30H
Test Codes
?
LRC CHEC
0DH
41H
41H
0AH
END
35H
35H
33H
33H
37H
DATA
37H
DATA
?
?
?
LRC CHECK
?
LRC CHECK
0DH
0DH
0AH
END
0AH
END
RTU Mode
Instruction Message Response Message (Normal) Response Message (Fault)
SLAVE Address 01 H
SLAVE Address
01H
SLAVE Address
01H
Function Code
08H
Function Code
08H
Function Code
88H
High 00H
High
00H
Error
Code
20H
Test
Codes
Low 00H
Test
Codes
Low
00H
High
47H
High A5H
High
A5H
CRC-16
Low
D8H
DATA
Low 37H
DATA
Low
37H
High DAH
High
DAH
CRC-16
Low 8DH
CRC-16
Low
8DH
