MOV DX,303H 
  MOV AL,80H 
  OUT DX,AL
AGAIN: MOV DX,300H 
  MOV AL,55H
  OUT DX,AL
  INC DX 
  OUT DX,AL
  CALL HSDELAY 
  MOV DX,300H 
  MOV AL,0AAH
  OUT DX,AL
  INC DX 
  OUT DX,AL
  CALL HSDELAY 
  MOV AH,01
  INT 16H 
  JZ AGAIN 
  MOV AH,4CH 
  INT 21H 
  HSDELAY PROC NEAR
  MOV CX,33144 
  PUSH AX
W1: IN AL,61H
  AND AL,00010000B
  CMP AL,AH
  JE W1
  MOV AH,AL
  LOOP W1
  POP AX
  RET
  HSDELAY ENDP