Motorola DS9808 - Symbol - Wired Handheld Barcode Scanner, Product Reference Manual

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10 - 30 Symbol DS9808 Product Reference Guide
Product Add Right to Left Simple Remainder
Each character in the scanned data is assigned a numeric value (see OCR Check Digit Multiplier on page 10-26 ).
The check digit multiplier is reversed in order. Each value representing a character in the scanned data is multiplied
by its corresponding digit in the reversed multiplier, resulting in a product for each character in the scanned data.
The sum of these products
except for the check digit's product
is computed. The check digit passes if this sum
modulo Check Digit Modulus is equal to the check digit's product.
Example:
Scanned data numeric value is 122456 (check digit is 6)
Check digit multiplier string is 123456
Digit 1 2 2 4 5 6
Multiplier 6 5 4 3 2 1
Product 6 10 8 12 10 6
Product add 6+ 10+ 8+ 12+ 10= 46 6
The Check Digit Modulus is 10. It passes because 46 divided by 10 leaves a remainder of 6.
Product Add Right to Left Simple Remainder
(05h)