calculating one byte checksum

[assaad]

Hi all
I could not find how to calculate one byte checksum to communicate with laser sensor via usart.
The laser sensor accept 4 bytes and one byte check sum.
There is an example in the manual:
7E F1 81 03 8A
Where 8A is the check sum? Could anyone explain how they calculated 8A?

Regards

[PCM programmer]

Well, tell us what CCS manual it's in. Tell us the section or the page
that it's on.

Or if you don't mean the CCS manual, but instead you mean the sensor
manual, then post a link to the sensor manual. (And the page number).