Instruction Set DAA
DAA -- Decimal Adjust AL after Addition
DAA -- Decimal Adjust AL after Addition
Opcode Instruction Clocks Description
27 DAA 4 Decimal adjust AL after addition
Operation
IF ((AL AND 0FH) > 9) OR (AF = 1)
THEN
AL = AL + 6;
AF = 1;
ELSE
AF = 0;
FI;
IF (AL > 9FH) OR (CF = 1)
THEN
AL = AL + 60H;
CF = 1;
ELSE CF = 0;
FI;
Description
Execute DAA only after executing an ADD instruction that leaves a
two-BCD-digit byte result in the AL register. The ADD operands should
consist of two packed BCD digits. The DAA instruction adjusts AL to
contain the correct two-digit packed decimal result.
Flags Affected
AF and CF as described above; SF, ZF, PF, and CF as described in
Appendix C.
Protected Mode Exceptions
None
Real Address Mode Exceptions
None
Virtual 8086 Mode Exceptions
None