The Knowledge Adda

Assumption: We have to write a program to unpack the BCD numbers is stored in memory locations 2200 H and we have to store output at memory location 2300 and 2301 H.

 

Algorithm:

Program:

Memory Address	Op-code	Operand	Comments
2000	LDA	2200H	Load Packed Number in A
2003	ANI	F0H	Mask the lower order nibble
2005	RRC		Rotate A right without carry
2006	RRC
2007	RRC
2008	RRC
2009	STA	2300 H	Store the partial result
200C	LDA	2200 H	Load Number in accumulator
200F	ANI	0F H	Mask higher byte nibble
2011	STA	2301 H	Store the result
2014	RST	5	Set Break-point(optional)
2015	END		End the program

Used Instruction:

LDA address: Load data into register A (accumulator) directly from the address given within the instruction.

RRC: Each binary bit of the accumulator is rotated right by one. Bit D7 is placed in the position of B0 as well as carry flag.

ANI: This instruction logically ANDs the 8-bit data given in the instruction with the contents of accumulator and stores the result in the accumulator.

MOV: This instruction is used to copy the content from source register to destination register.

ADD: This instruction is used to add the content of specified register to the content of accumulator and store output in accumulator.

STA: This instruction is used to store the content of accumulator at specified memory address.

RST 5: This instruction is used to set break-point for the execution.

END: This instruction is used to execute the program.

 

Result:

Input: 2200 H-31 H

Output:

2300 H-01 H

2301-03 H             

 

Procedure to look output