What is the purpose of DAA instruction?
The DAA instruction is only useful when it follows an ADD instruction that adds (binary addition) two 2-digit, packed BCD values and stores a byte result in the AL register. The DAA instruction then adjusts the contents of the AL register to contain the correct 2-digit, packed BCD result.
What are the flags affected due to DAA instruction?
What are the flags affected due to DAA instructions? Flags Affected ¶ The CF and AF flags are set if the adjustment of the value results in a decimal carry in either digit of the result (see the “Operation” section above). The SF, ZF, and PF flags are set according to the result.
Which of the following instruction is used in decimal addition?
decimal adjust instruction
Answer: The decimal adjust instruction is used to obtain correct results of decimal addition or subtraction.
What is BCD in microprocessor?
In computing and electronic systems, binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each digit is represented by a fixed number of bits, usually four or eight. Sometimes, special bit patterns are used for a sign or other indications (e.g. error or overflow).
How do you handle DAA instruction show with an example?
All that is required to be done is to add the BCD numbers and store the result in A, and then execute the DAA instruction. If the LS hex digit in A is <= 9 and AC flag is 0, the LS hex digit value will not be altered. If the LS hex digit is >9, or if AC flag is set to 1, it adds 6 to the LS hex digit of A.
When to run the DAA instruction in Excel?
DAA is intended to be run immediately after an addition or subtraction operation, where the operands were BCD encoded. It then makes the corrections described above, so the result (stored in the A register) is the BCD encoded result of the previous operation.
When to use DAA in the AL register?
Use daa only after executing the form of an add instruction that stores a two-BCD-digit byte result in the AL register. daa then adjusts AL to a two-digit packed decimal result.
When to use DAA in a BCD program?
daa. The daa instruction is used to adjust the content of the AL register after that register is used to perform the addition of two packed BCDs. The CPU uses the following logic: CF_old = CF IF (al AND 0Fh > 9) or (the Auxilliary Flag is set) al = al+6
Where does the DAA instruction set the flags?
On a Z80, at least, the DAA instruction sets a couple of flags based on the final value. The logic for these is at the end of the function. Flag Condition