ICP DAS USA I-7530-G CR User Manual page 27

The checksum [CHK] is 2-characters of the sum of the command
message, from first character to the character before <CR>. When
calculate checksum, the value of [CHK] is zero.
For example:
Command: Reboot the I-7530 module, "RA[CHK]<CR>".
1. Sum of the string = 'R' + 'A' = 52h + 41h = 93h.
2. Therefore the checksum is 93h and so [CHK]="93".
3. The command string with checksum ="RA93<CR>".
I-7530 RS-232/CAN Converter User's Manual (Version 2.5, Mar/2012) ------------- 27