Pages created and updated by
Terry Sturtevant
Date Posted:
November 13, 2013

**Binary Coded Decimal (BCD) Arithmetic**

- decimal numbers are coded in binary
- for PIC, arithmetic operations assume packed BCD with 2 decimal digits per 8 bits

e.g. decimal 1,985 = h'19 85' in packed BCD

= 0001 1001 1000
0101 (in binary)

e.g. 19 85 0001 1001 1000 0101

+34 59 0011 0100
0101 1001

------ ------------------------

54 44 0100
1101 1101 1110 >> the binary sum does not give the decimal result
expected

0110 0110 0110 >> if
a digit is >9 then add 6

------------------------

0101
0100 0100 0100 >> result is now in binary coded decimal

In the PIC, use add/addc followed with decimal adjust, daw/dawc.

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