YOKOGAWA UPM100, User Manual

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5-13
IM 77C01H01-10EN
MODBUS Communication
5
5.2 Message and Response
08 Performs loop back test
Function
This function code is used to check connection for communication.
• For the format of response in the event of failure, see subsection 5.1.4.
• The “00” shown below (marked with an asterisk *) are fixed.
• Any value can be selected for send data.
Message (for normal operation)
Element
Start of
Message Mark
(:)
Station
Number
(ST-NO)
Function Code
(08)
00*
0000
Send Data
(Arbitrary)
Number of bytes
in RTU mode
None 1 1 2 2
Number of bytes
in ASCII mode
1 2 2 4 4
Message (continued)
Error Check
End of
Message Mark
(CR + LF)
2 None
2 2
Response (for normal operation)
Element
Start of
Message Mark
(:)
Station
Number
(ST-NO)
Function Code
(08)
00
0000
Same as Send
Data
Number of bytes
in RTU mode
None 1 1 2 2
Number of bytes
in ASCII mode
1 2 2 4 4
Response (continued)
Error Check
End of
Message Mark
(CR + LF)
2 None
2 2
Diagnostic Codes
Diagnostic Code Meaning Data
0000 Command message return Arbitrary
Example (ASCII mode)
Send data “0000” (fixed) and send data 04D2 (arbitrary) to the station number 11 to check
the connection for communication.
[Message] [:]0B08000004D217[CR][LF]
When the connection is normal, the following response same as the command is returned.
[Response] [:]0B08000004D217[CR][LF]