4 Bytes one button press

[Dennis]

Hi Art

Thanks so much that's a very helpful tip indeed!

I haven't tried this yet but I will as soon as I get a chance and feedback asap.

Just curious if I need to declare CHECKSUM as a byte or a word ?
For example if the byte is 255 Decimal aka 11111111 Binary, would there be any overflow into a second byte

Kind regards

Dennis

[Art]

The checksum is a byte.
If you XOR a number with any other number, there can never be an overflow.

The XOR operation tests each bit of the two bytes operated on.
If the first two bits of each value are the same, the first bit of the new byte is 0.
If the first two bits of each value are different, the first bit of the new number is 1.

0000111 XOR
1010101 =

1010010

[Dennis]

Hi Art

Once again thanks for the explanation and reply :-)

Mmm the eXclusive OR so the truth table then looks like this ...

A B Result
1 1 0
1 0 1
0 1 1
0 0 0

So ....
The XOR operator returns a 1 when the value of either the first bit or the second bit is a 1.

The XOR operator returns a 0 when neither or both of the bits is 1.

And for a variable swap we could do something like this then ?
X var byte
y var byte

x = x xor y
y = x xor y
x = x xor y

which would be something to consider but NOT to do :-) (just wondering how PBP would react to that one ?)
See here:
http://betterexplained.com/articles/...les-using-xor/
and here:
http://www.topbits.com/xor-encryption.html

Thanks so much one again
Will definitely give it a bash and post some feedback of the results :-)

Kind regards

Dennis

[Dennis]

Hi Art

Once again thanks for the explanation and reply :-)

Mmm the eXclusive OR so the truth table then looks like this ...

A B Result
1 1 0
1 0 1
0 1 1
0 0 0

So ....
The XOR operator returns a 1 when the value of either the first bit or the second bit is a 1.

The XOR operator returns a 0 when neither or both of the bits is 1.

And for a variable swap we could do something like this then ?
X var byte
y var byte

x = x xor y
y = x xor y
x = x xor y

which would be something to consider but NOT to do :-) (just wondering how PBP would react to that one ?)
See here:
http://betterexplained.com/articles/...les-using-xor/
and here:
http://www.topbits.com/xor-encryption.html

Thanks so much once again!

Will definitely give it a bash and post some feedback of the results :-)

Kind regards

Dennis