Hello to everyone, I need some help with CRC... or checksum
Here is just 1am, but I am stuck!

I need to calculate maybe checksum from a data stream, I have some information for it, but I can not figure it out how to work with.

From the documentation that I have, this is the information


" The data at ascii is this $P;aa;bbbbb;cc;d;eeeeeeeee;crc
a : 2 bytes
b : 5 bytes
c : 2 bytes
d : 1 byte
e : 9 bytes
crc: Chksum 3 bytes (EXCLUSIF) "


and some real examples here:
$P;21;00987;10;3;000075991;191 (hex: 24 50 3B 32 31 3B 30 30 39 38 37 3B 31 30 3B 33 3B 30 30 30 30 37 35 39 39 31 3B 31 39 31)
or
$P;22;00000;00;0;002413651;189 (hex: 24 50 3B 32 32 3B 30 30 30 30 30 3B 30 30 3B 30 3B 30 30 32 34 31 33 36 35 31 3B 31 38 39)
or
$P;21;00000;00;0;000144924;182 (hex: 24 50 3B 32 31 3B 30 30 30 30 30 3B 30 30 3B 30 3B 30 30 30 31 34 34 39 32 34 3B 31 38 32)


At the first example the crc is 191 (ascii), at the second is 189 and at the third is 182

According the small documentation that I have, this checksum or crc (I know that is something entirely different) is calculate with Xor,
but I cant find how.

Can anyone help me about?

Thank you for your time

Nick