DAA Decimal Adjust after Addition Flags: O D I T S Z A P C
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DAA
Logic: If (AL & 0Fh) > 9 or (AF = 1) then
AL AL + 6
AF 1
else AF 0
If (AL > 9Fh) or (CF = 1) then
AL AL + 60h
CF 1
else CF 0
DAA corrects the result of a previous addition of two valid packed
decimal operands (note that this result must be in AL). This
instruction changes the content of AL so that it will contain a pair
of valid packed decimal digits.
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Operands Clocks Transfers Bytes Example
no operands 4 - 1 DAA
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Note: Packed BCD stores one digit per nibble (4 bits); the
least significant digit is in the lower nibble.
It is not possible to apply an adjustment after
division or multiplication of packed BCD numbers.
If you need to use multiplication or division, it is
better to use unpacked BCD numbers. See, for
example, the description of AAM (ASCII Adjust after
Multiply).
Seealso:
This page last updated on Fri Nov 30 10:49:50 MSK 2001
Copyright © 1992-2001, Vitaly Filatov, Moscow, Russia
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