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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