NEC MultiSync P402, Руководство пользователя

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4.3 Check code
Check code is the Block Check Code (BCC) between the Header and the End of Message except SOH.
D
n+1
= D
1
XOR D
2
XOR D
3
XOR ,,, D
n
XOR: Exclusive OR
Following is an example of a Check code (BCC) calculation.
Check code (BCC) D
17
= D
1
xor D
2
xor D
3
xor
…
xor D
14
xor D
15
xor D
16
= 30h xor 41h xor 30h xor 45h xor 30h xor 41h
xor 02h xor 30h xor 30h xor 31h xor 30h xor 30h
xor 30h xor 36h xor 34h xor 03h
= 77h
Header Message Check code Delimiter
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
SOH D
0
Reserved D
1
Destination D
2
Source D
3
Type D
4
Length(H) D
5
Length(L) D
6
STX D
7
Data D
8
| |
| |
ETX D
n
Check code D
n+1
P P P P P P P P
Header Message
SOH Reserved
Destination
Address
Source
Address
Message
type
Message length STX
OP code
page
OP code Set Value ETX
Check
code
(BCC)
Delimiter
01 30 41 30 45 30 41 02 30 30 31 30 30 30 36 34 03 77 0D
D
0
D
1
D
2
D
3
D
4
D
5
D
6
D
7
D
8
D
9
D
10
D
11
D
12
D
13
D
14
D
15
D
16
D
17
D
18