Can Anybody solve this data pattern??

[ex4]

Hello
i got stream of data like this, but i'm rather confused about the last byte (F3)
can anybody help solve this??? all data in hexadecimal format and the spaces just to make easy looking of the data stream

53 01 03 49 90 04 F3
53 02 03 49 90 04 F3
53 03 03 49 90 04 F3

53 01 03 50 37 04 12
53 02 03 50 37 04 12
53 03 03 50 37 04 12

53 01 03 00 20 04 84
53 02 03 00 20 04 84
53 03 03 00 20 04 84

 

[Anno]

I don;t understand, if it is in hex, then it is normal to receive a byte with F3 = 243 in decimal?

 

[tronix]

Well can u explain a bit further ex4

 

[ex4]

well F3, 12 and 84 is kind a checksum error of the data
but i need the general formula of this value based on the other value.
as you could see that only the second byte that changes and the other don't.
so any idea about the formulation???
:?::?:

 

[Anno]

mmm....jou don't know what kind of checksum they are using, ther e is quite a few checksum algorithms if i'm not mistaken.
Ussually checksums are computed in binary. convert it and see if it helps

 

[ex4]

well it makes no good at all