The Knowledge Adda

Apparatus Used: Microprocessor Kit, Keyboard

Assumption: In 8085, the contents of flag register and the accumulator together are called program status word (PSW). The PSW can be accessed by only using PUSH and POP instructions. The PUSH instructions move the flag register contents (as lower byte order) and the accumulator contents (as higher byte order) of the stack.

 

Algorithm:

Program:

Memory Address		Op-code	Operand	Comments
2000	PUSH		PSW	Push the contents of A and Flag in Stack
2003	POP		H	Store PSW in H-L pair
2004	MOV		A,L	Move the contents of Flag Register in A
2007	CMA		A,E	Complement the Accumulator
2009	MOV		L,A	Store complemented flag in register L
200A	PUSH		H	Push the contents of HL pair onto stack
2010	RST		5	Set Break Point(Optional)
2011	END			End the program

Used Instruction:

PUSH: This instruction pushes the contents of the register pair onto a stack.

POP: Pops the top two memory locations on the stack on a register pair.

MOV rd, rs: This instruction copies data from the source register into destination register.

CMA: Complements the contents of accumulator.

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

END: This instruction is used to execute the program.