Initialisation of Interrupt

START2:
MOV SP,#31H
MOV IE,#85H
CLR IT0


Interrupt Service Routine is as below

EXTERNAL_INTERRUPT:

      MOV P0,#0FFH
      MOV P1,#0FFH
      MOV P3,#4FH
      CALL CLEAR_LCD
      CALL EMERGENCY_STOP_TEXT
      
      LJMP MAIN
      
      RETI