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MELSEC-
A
7 USING FRAMES WHEN EXCHANGING DATA
3) Transmission/reception data corresponding to FAH
The user registration frame section corresponding to the special
character code FA
H converts the sum check code calculated using the
range including the user registration frame (head frame) of the
transmission/reception data (statement) into a complement of 2. The
low-order 1 byte of the converted value is expressed as ASCII data
and then transmitted/received.
•
Calculation range (Refer to 2).)
•
Calculating the sum check code
This is the value obtained adding the data in the above range as
binary data and converting it into a complement of 2.
(In case of example 2))
(H)(L)
02H + 10H + 41H + 31H + ABH + 12H + 03H = 0144H
15
0144
H
0
14
0
13
0
12
0
11
0
10
0
9
0
8
1
7
0
6
1
5
0
4
0
3
0
2
1
1
0
0
0
FEBB
H
1
14 13 12 11 10 9 8
0
7
1
6
0
5
1
4
1
3
1
2
0
1
1
0
1
15
FEBC
H
1
14
1
13
1
12
1
11
1
10
1
9
1
8
0
7
1
6
0
5
1
4
1
3
1
2
1
1
0
0
0
111111
A
ddition value
Reversal
(Complement of 1)
+1
(Complement of 2)
The low-order 1 byte section ("B""C") of the complement of 2 (FEBCH)
for 0144
H is transmitted/received from "B".
POINT
•
When receiving a registration frame containing a sum check code, if the values of the
received sum checks do not match, a "sum check error (BB28
H)" will occur.
•
When transmitting a registration frame containing a special character for sum check codes, it
can be used only for the end frame transmitted with the transmission frame 1 area.
The frame cannot be used for the end frame of transmission with the transmission frame 2
area.
•
Designation of only a special character for the sum check code in the user registration frame
is not possible.
•
When transmitting/receiving sum check codes, set the RS-232-C data bit length to 8 bits.
•
Multiple sum checks cannot be used in one user registration frame.
•
If ASCII/binary conversion is designated, when transmitting, the data will be converted into
ASCII data and then the sum check will be calculated with the transmission data. When
receiving, the sum check will be calculated with the reception data before binary data
conversion.
R2
Buffer memory
(Transmission area/reception area)
ASCII data
External device
Binary
data
Conversion
At transmission
At reception