Omron S8AS, User Manual

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99
Variable Area Operations
Section 6-3
6-3 Variable Area Operations
Read Variable Area
This service reads data from a variable area.
■ Service Request PDU
■ Service Response PDU
(1) Variable Type and Read Start Address
The definitions are different for each product.
(2) Bit Position
The S8AS does not support bit access. Fixed at “00.”
(3) Number of Elements
Note (1) If the Read Start Address is outside of the variable area, the returned
read data will all be 0, but the specified number of elements will be re-
turned and the processing will end in “normal completion.”
(2) If the Read Start Address is within the variable area and the Read End
Address (Read Start A Number of Elements) is beyond the last
variable area address, the read operation will be performed as long as the
amount of data up to the last variable area address is within the specified
range of the number of elements. The read data beyond the end of the
variable area will all be set to 0. (See the following example.)
Reading Two Elements and Exceeding the Last Variable Area Address
In this case, the second element does not exist, so the read data will be
AAAA0000.
MRC SRC
0 1 0 1 0 0
2 2 2 4 2 4
Variable
Type
Read Start
Address
Bit
Position
Number of
Elements
MRC SRC
0 1 0 1
2 2 4
Response Code
Read Data
(for number of elements)
0 to 224
Number of
elements
Processing
0000 The read operation is not performed (read data is not
appended to the service response PDU), and processing ends
in “normal completion.”
0001 to 0038 The read operation is performed, and processing ends in “nor-
mal completion” (hexadecimal display).
AAAA
Read Start Address
→
Read End Address
→
←
Last address
Address Variable area
* * * * * * * *
* * * *