Write a program to sub 8 bit numbers in microprocessor 8085?

Answer 1

;A assembly program to reverse a number.

jmp start

;data

;code

start: nop

mvi e,0f0h; ;no. to be reversed

mvi d,00h; ;result

mvi c,11h; ;masking bits

mvi a,11h; ;to store the current mask

mvi h,04h; ;counter

mvi b,01h;

rev: ana e; ;using the mask

jz end;

mov l,a; ;temp storage for storing the bits

ani 0fh; ;storing the lsb's

mov a,l;

mov l,b;

shift: rrc;

dcr l;

jnz shift;

ora d;

mov d,a;

end: mov a,c;

rlc;

mov c,a;

inr b;

inr b;

dcr h;

jnz rev;

hlt

Answer 2

Sample problem:

(4000H) = 51H

(4001H) = 19H

Result = 51H - 19H = 38H

Source program:

LXI H, 4000H : HL points 4000H

MOV A, M : Get first operand

INX H : HL points 4001H

SUB M : Subtract second operand

INX H : HL points 4002H

MOV M, A : Store result at 4002H.

HLT : Terminate program execution