Sub routine to perform the task of DAA

Statement: Assume the DAA instruction is not present. Write a sub routine which will perform the same task as DAA.

Sample Problem:
Execution of DAA instruction:
1. If the value of the low order four bits (03-00) in the accumulator is greater than 9 or if auxiliary carry flag is set, the instruction adds 6 '(06) to the low-order four bits.
2. If the value of the high-order four bits (07-04) in the accumulator is greater than 9 or if carry flag is set, the instruction adds 6(06) to the high-order four bits.


Source program :

• LXI SP, 27FFH : Initialize stack pointer
• MOV E, A : Store the contents of accumulator
• ANI 0FH : Mask upper nibble
• CPI 0A H : Check if number is greater than 9
• JC SKIP : if no go to skip
• MOV A, E : Get the number
• ADI 06H : Add 6 in the number
• JMP SECOND : Go for second check
• SKIP: PUSH PSW : Store accumulator and flag contents in stack
• POP B : Get the contents of accumulator in B register and flag register contents in C register
• MOV A, C : Get flag register contents in accumulator
• ANI 10H  : Check for bit 4
• JZ SECOND  : if zero, go for second check
• MOV A, E  : Get the number
• ADI 06 : Add 6 in the number
• SECOND: MOV E, A : Store the contents of accumulator
• ANI FOH : Mask lower nibble
• RRC 
• RRC
• RRC
• RRC : Rotate number 4 bit right
• CPI 0AH : Check if number is greater than 9
• JC SKIPl  : if no go to skip 1
• MOV A, E : Get the number
• ADI 60 H  : Add 60 H in the number
• JMP LAST : Go to last
• SKIP1: JNC LAST   : if carry flag = 0 go to last
• MOV A, E : Get the number
• ADI 60 H  : Add 60 H in the number
• LAST: HLT