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FX Series PLC User's Manual - Data Communication Edition
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6. Sum check code
The sum check code indicates a two-digit ASCII code converted from the least significant byte (8-bit) of the
sum check target data added as hexadecimal data.
Using the FX PLC parameters, set whether or not the sum check code is added in the message.
- When "sum check code provided" is selected, the sum check code is added in the message during
sending. During receiving, the sum check code is compared with the value calculated from the received
data to check the received data.
- When "sum check code not provided" is selected, the sum check code is not added, so the received
data is not checked either. A calculation example of the sum check code is shown below.
Example: When the station number "0", PLC number "FF", command "BR (device memory batch read)",
message waiting time "30 ms" and data "ABCD" are transferred in format 1, the sum check code
value is as shown below:
Computer side
PLC side
30
+30
H
Total from "station number" to "character area"
D-52
Station
PLC
E
No.
No.
N
Q
0 0
F F
05
30
30
46
46
H
H
H
H
+46
+46
+42
+52
+33
+41
H
H
H
H
H
H
Mes-
Com-
Character area
sage
mand
wait
time
A B C D
B R
3
42
52
33
41
42
43
44
H
H
H
H
H
H
H
H
+42
+43
+44
=2BD
H
H
H
H
H
Last two
digits
6 Control Procedures and Setting Methods
6.4 Basic Formats of Dedicated Protocol
Sum
check
code
B D
42
44
H
H
S
T
0 0
F F
X
02
30
30
46
46
H
H
H
H
30 ms
(Message waiting time)
. . .
H
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