Check Code - NEC MultiSync V423 Manual

4.3 Check code

Check code is the Block Check Code (BCC) between the Header and the End of Message except SOH.
D = D XOR D
n+1 1 2
XOR: Exclusive OR
Following is an example of a Check code (BCC) calculation.
Destination
SOH Reserved
Address
01 30 41
D D D
0 1 2
Check code (BCC) D
Header
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
XOR D XOR ,,, D
3 n
Header
Source Message
Message length
Address type
30 45 30
D D D
3 4 5
= D xor D
17 1
= 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
Message Check code
7 6 5 4
2 2 2 2
P P P P
OP code
STX
page
41 02 30 30
D D D D
6 7 8 9
xor ... xor D
xor D
2 3 14
(11/72)
Delimiter
3 2 1 0
2 2 2 2
P P P P
Message
OP code Set Value
31 30 30 30 36 34
D D D D D D
10 11 12 13 14 15
xor D xor D
15 16
Check
code Delimiter
ETX
(BCC)
03 77 0D
D D D
16 17 18