ORG 00H
LJMP MAIN
MAIN:

MOV P1,#0FFH
MOV P3,#0FFH

STAY:     / wait for p3.1 to go down before running

  JB P3.1,STAY
  
CLR P3.0   / signal to "enable pin" of L293N

CALL DELAY

HERE:      / signal sequence with some delay, if i decrease 
             this delay too much the motor does not run

MOV A,#33H

MOV P1,A

CALL DELAY

RR A

MOV P1,A

CALL DELAY

RR A

MOV P1,A

CALL DELAY

RR A

MOV P1,A

CALL DELAY

JMP HERE

DELAY:

   MOV R1,#09H

LOOP2:

   MOV R2,#07H

LOOP1:

   MOV R3,#0FFH 
 
LOOP:

   DJNZ R3, LOOP
   
   DJNZ R2, LOOP1 
   
   DJNZ R1, LOOP2
   
   RET