MOV AL,80H
  MOV DX,CNTRLPORT 
  OUT DX,AL 
  MOV BL,33H
AGAIN:MOV AH,01
  INT 16H 
  JNZ EXIT 
  MOV AL,BL
  MOV DX,PORTA
  OUT DX,AL
  MOV CX,20000
HERE: LOOP HERE 
  ROR BL,1
  JMP AGAIN
EXIT: