Check Code - NEC LCD Monitor 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.
SOH Reserved Destination
Address 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
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
STX OP code
page
41 02 30 30 31 30 30 30 36 34
D D D D
6 7 8 9
xor ... xor D
xor D
2 3 14
(13/137)
Delimiter
3 2 1 0
2 2 2 2
P P P P
Message
OP code Set Value
D D D D D D
10 11 12 13 14 15
xor D xor D
15 16
Check Delimiter
code
ETX
(BCC)
03 77 0D
D D D
16 17 18