This I use and it works well:
Code:
Start:

OWOUT DQ, 1, [ $33 ]                 'send read Rom command

OWIN DQ, 2, [ FaM,skip 7]            'read sensor family code, skip ID and CRC
   if FaM = $28 then SkipOver        'if FaM = 28 then sensor is present

     LCDOUT $FE,$80,        "NO SENSOR "
     LCDOUT $FE,$C0,        "Chk Sens & Reset"

   goto Start                              'sensor not present so do again

SkipOver:                                  'continue your code here
Regards
Hebe