YOKOGAWA UPM100, Руководство пользователя

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5-11
IM 77C01H01-10EN
MODBUS Communication
5
5.2 Message and Response
03 Reads data from multiple D registers
Function
This function code reads the contents of successive D registers by the specified number
starting from a specified D registers number.
• The maximum number of D registers to be read at a time is 64.
• For the format of responses in the event of failure, see subsection 5.1.4.
Message (for normal operation)
Element
Start of
Message Mark
(:)
Station
Number
(ST-NO)
Function Code
(03)
D-Register
Start Number
Number of
D Registers
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
(03)
Byte
Count
Contents of
D Register
...
Number of bytes
in RTU mode
None 1 1 1 2 ...
Number of bytes
in ASCII mode
1 2 2 2 4 ...
Response (continued)
Contents of
D Register
Error Check
End of
Message Mark
(CR + LF)
2 2 None
4 2 2
Example (ASCII mode)
Read a series of four D registers starting with the D0043 (VT ratio and CT ratio) at station
number 11. (D register specification is “42.”)
[Message] [:]0B03002A0004C4[CR][LF]
“0B”:station number 11, “03”: function code 03, “002A”: D register specification 42, “0004”:
number of D registers 4, and “C4”: error check
* Numbers in quotation marks are hexadecimal.
The following response is returned with respect to the above message.
[Response] [:]0B030800003F8000003F806C[CR][LF]
* The CT ratio and VT ratio are floating-point data. The two words of “D0044” and “D0043” indicate
“1.” This is the same for “D0046” and “D0045.” The order of the upper word “3F80” and lower
word “0000” are converted.
* 3F800000 (floating-point data) → 1 (decimal)