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4. COMMUNICATIONS USING A DEDICATED
PROTOCOL
MELSEC
QnA
F l
Sum check code
When a dedicated protocol format is used to send and receive data, the reliability of the
sendheceive data can be increased by sending and receiving the sum check code shown
below by setting switch SW06 (sum check code enable/disable setting) on the AJ71
QC24
to
ON.
If SW06 is set to ON, the AJ71
QC24,
0
adds a sum check code to the send data and sends the data,
@
checks the sum check code of the receive data.
In this guidebook, data is transmitted by setting SW06 to OFF. Therefore, the sum check
code is
not
handled.
The following uses an example to describe the contents of the sum check code for your
reference.
[Ex.] The following shows the sum check code value when the data of three points,
beginning from DO, is read for QnA frame format
1
station No.
0,
network No.
00,
PC
No. FF, local station
No.
00
command
0 4 0 1
(device memory word units batch
read).
Character area
-
*
46H+39H+30H+30Ht30H+3OH+46Ht46H+3OH
+30H+30H+34H+30H+31Ht3OH+3OH+44H+ZAH
+30H+30H+30H+30H+30H+3OH+3OH+3OH+3OH+33H=~
T
I
U
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