Instruction Manual

<Toc> <Ind> <5. MODBUS Communication >
5-9
IM 77J04J11-01E 1st Edition : 2006.08.25-00
08 Performs loop back test
● Function
This function code is used to check the connection for communication.
• For the format of response in the event of failure, see subsection 5.2.2.
• The element marked with * is "00" (fixed).
• Any value can be selected for send data.
● Message (for normal operation)
211None
4221
Number of bytes in RTU mode
Number of bytes in ASCII mode
2
4
Address
Number
(ADR)
Start of
Message Mark
(:)
Element Function
Code (08)
00*
0000
Send Data
(any)
Message (continued)
Error
Check
End of Message
Mark (CR+LF)
None2
22
● Response (for normal operation)
211None
4221
Number of bytes in RTU mode
Number of bytes in ASCII mode
2
4
Address
Number
(ADR)
Start of
Message Mark
(:)
Element Function
Code (08)
00
0000
Same as
send data
Response (continued)
Error
Check
End of Message
Mark (CR+LF)
None2
22
● Example:
Sending data 1234 (HEX) to the M Series with address number 01 to check connection for
communication.
The following message sends 1234 (HEX) to address number 01 in the ASCII mode.
[Message]
: 010800001234B1[CR][LF]
Start of message mark
When the connection for communication is normal, the response whose configuration is the
same as that of the message is returned with respect to the above message.
[Response]
: 010800001234B1[CR][LF]