Azbil AUR355 - Fixed Length Consecutive Data Read Command (RD Command)

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Chapter 4. Communication

Fixed length consecutive data read command (RD command)
This command reads continuous data in two-byte units. This command is suitable
for handling data in ladder programs sent by PLC communications because the
data has a fixed length.
The data start address is expressed as four hexadecimal digits for RD. The number
of data words to read is expressed as four digits, and data is expressed as four × n (n
is a positive integer) hexadecimal digits.
z
Command message
The read start address (four hexadecimal digits) and the number of data words to
read (four hexadecimal digits) are sent.
(1) Command
(2) Data start address
(3) Number of data records
R
(1)
D
(2) (3)
z
Response message
If the command is successful, the end code is Normal (two decimal digits) and
is returned with the specified number of data words (four hexadecimal digits ×
number of data words to read) appended. If there was an error, the Error end code
(two decimal digits) is returned without read data appended.
0

Normal end (reading of single data record)
(1)
0

Normal end (reading of multiple data records)
0
(1)
0
(2) (3) (4)

Abnormal end
X
(1)
X
The end code (error) is entered in place of XX.
(2)
(1) End code
(2) Data 1
(3) Data 2 to (n−1)
(4) Data n