Mitsubishi MELSEC LJ71C24, Руководство пользователя

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App. - 49 App. - 49
APPENDIXES
(3) Procedure for calculating sum check
The following show procedures for calculating sum check codes using the
following sample data.
STX "J" "7" "1" "C" "2" "4" "N" ETX
Calculating range
"Q"
Sum
check
(For the data shown above)
Sum check = 51
H
+ 4A
H
+ 37
H
+ 31
H
+ 43
H
+ 32
H
+ 34
H
+ 4E
H
+ 03
H
= 1FD
H
(a) Data flow: Forward direction
1) "Complement calculation" is 'No complement calculation'
(1FD
H
in hexadecimal is 509 in decimal)
Data length
Code type
1 byte 2 bytes 3 bytes 4 bytes
ASCII
hexadecimal "D"
(44
H
)
"FD"
(46
H
44
H
)
"1FD"
(31
H
46
H
44
H
)
"01FD"
(30
H
31
H
46
H
44
H
)
ASCII decimal
"9"
(39
H
)
"09"
(30
H
39
H
)
"509"
(35
H
30
H
39
H
)
"0509"
(30
H
35
H
30
H
39
H
)
HEX FD
H
01FD
H
0001FD
H
000001FD
H
2) "Complement calculation" is 'One's complement'
(One's complement of 0000 01FD
H
is FFFF FE02
H
)
When "Code type" is 'ASCII decimal', the last one word is extracted
and converted from hexadecimal to decimal.
(FF02
H
in hexadecimal is 65026 in decimal)
Data length
Code type
1 byte 2 bytes 3 bytes 4 bytes
ASCII
hexadecimal "2"
(32
H
)
"02"
(30
H
32
H
)
"E02"
(45
H
30
H
32
H
)
"FE02"
(46
H
45
H
30
H
32
H
)
ASCII decimal
"6"
(36
H
)
"26"
(32
H
36
H
)
"026"
(30
H
32
H
36
H
)
"5026"
(35
H
30
H
32
H
36
H
)
HEX 02
H
FE02
H
FFFE02
H
FFFFFE02
H
3) "Complement calculation" is 'Two's complement'
(Two's complement of 0000 01FD
H
is FFFF FE03
H
)
When "Code type" is 'ASCII decimal', the last one word is extracted
and converted from hexadecimal to decimal.
(FE03
H
in hexadecimal is 65027 in decimal)
Data length
Code type
1 byte 2 bytes 3 bytes 4 bytes
ASCII
hexadecimal "3"
(33
H
)
"03"
(30
H
33
H
)
"E03"
(45
H
30
H
33
H
)
"FE03"
(46
H
45
H
30
H
33
H
)
ASCII decimal
"7"
(37
H
)
"27"
(32
H
37
H
)
"027"
(30
H
32
H
37
H
)
"5027"
(35
H
30
H
32
H
37
H
)
HEX 03
H
FE03
H
FFFE03
H
FFFFFE03
H