DAA Decimal Adjust Accumulator Instruction
This instruction adjusts the contents of the accumulator into BDC (Binary Coded Decimal ) form after a BCD addition. It should be used after ADD, ADI etc instruction if performing BCD addition the instruction format is
DAA
This is the only instruction which uses auxiliary carry flag internally.
Flag: All flags are moodier according t the result.
Followings procedure is used by DAA instruction to convert the contents of th e accumulator from binary to BCD.
a.If the value of low order four bits (D3 -D0) in the accumulator of the accumulator 9 the instruction adds 6 to the low order four bits.
b.If the value of high order four bits (D7-D4) in the accumulator is more than 9 the instruction adds 6 to the high order four bits
See followings example to understand the working of DAA instruction.