GPS-721 User Manual
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GPS-721 User Manual V2.0, Oct. 2010
Checksum Calculation:
1. Calculate the ASCII code sum of all the characters in the
command/response string, except for the carriage return
character (CR).
2. The checksum is equal to the sum masked by 0FFh.
Example
：
：
：
：
Command string: $012(CR)
1. Sum of the string = “$”+”0”+”1”+”2” = 24h+30h+31h+32h = B7h
2. Therefore the checksum is B7h, and so CHKSUM = “B7”
3. The command string with the checksum = $012B7(CR)
Response string: !01200600(CR)
1. Sum of the string = “!”+”0”+”1”+”2”+”0”+”0”+”6”+”0”+”0” =
21h+30h+31h+32h+30h+30h+36h+30h+30h = 1AAh
2. Therefore the checksum is AAh, and so CHKSUM = “AA”
3. The response string with the checksum = !01200600AA(CR)
Note: All characters should be in upper case.
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