It is as simple as:

Code:
' Read iButton Family Code & Serial Number

        TempA var byte[8]   
        iButton Var PortB.0 ' iButton connected to PortB.0
        
        OWOUT iButton,1,[$33] ' Issue Read ROM command
        Pause 100
        'Read 64 Bits (8 Bytes) into Array TempA
        OWIN iButton,0,[TempA[0],TempA[1],TempA[2],TempA[3],TempA[4],TempA[5],TempA[6],TempA[7]]
For Reference see DS1990 Datasheet