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4-14
Chapter 4. CPL Communication
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WD command (hexadecimal format consecutive data write)
z WD command instruction message
This is a command—in one message—to consecutively write fixed-length data
in hexadecimal format to multiple consecutive data addresses starting from the
specified start data address. This command is suitable for handling data in ladder
programs sent by PLC communications as the data is of a fixed length.
The application layer of the write instruction consists of the following three types of
data.
Write instruction code
Write start data address
1st data record to write
2nd data record to write
02H 30H 31H 30H 30H 58H 57H 44H 30H 33H 45H 39H 30H 30H 30H 32H 30H 30H 34H 31H 03H 44H 46H 0DH 0AH 0AH
STX 0 1 0 0 X W D 0 3 E 9 0 0 0 2 0 0 4 1 ETX D F CR LF LF
Data link layer Application layer Data link layer
• It is not necessary to specify the number of data records to write.
• Use capital letters in character codes for all numbers and characters in the
application layer.
• Each value is expressed as a four-digit hexadecimal number.
• Since the data length is fixed, commas are not used to delimit the data.
• The figure above shows an example of an instruction message used to write
“0002” and “0041” (2 and 65 in decimal format) to addresses “03E9” and “03EA”
respectively.
1. Write instruction code (WD)

Role : This is a command for writing fixed-length data in hexadecimal
format.

Description : Two characters, "WD" (57H, 44H).
2. Write start data address

Role : This specifies by a four-digit hexadecimal number the data address
at which to begin writing.
6 - 2 Communication Data Table (p. 6-3) (for the relationship
between data addresses and write data)
Do not add “W” (57H) to the end of the data address.
3. Write data

Role : This is the data, expressed in four-digit hexadecimal numbers, that
is written to consecutive data addresses starting from the specified
data address.