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Thread: Difference Between testBit/setBit and variable.bitNumber

  1. #1
    Join Date
    08.05.2018
    Posts
    6

    Frage Difference Between testBit/setBit and variable.bitNumber

    Hi ,
    Suppose that i have a word variable like xWord (which is imported from OPC server) and i want to read or set some of its bits.(in following example, xbit is an internal zenon variable which is visible in Scada Logic) What's the difference between following approaches ? :

    1- xbit1  :=testBit(xWord ,1);  //(For reading second bit or bit number 1 )
        xWord := setBit(xWord,2, xbit2); //(For setting third bit or bit number 2 of xWord. This should change value of original xWord variable on the OPC and PLC)

        or :
    2-xbit1 := xWord.1 ;
       xWord.2 = xbit2 ;

    Thank you!

  2. #2
    Join Date
    01.07.2008
    Location
    Salzburg, AT
    Posts
    799
    Best Answer

    Default Re: Difference Between testBit/setBit and variable.bitNumber

    In case of your code - calling the FBs *Bit with a constant in the input BIT - there is no difference.

    The FBs *Bit are useful in the scenario when BIT input is a dynamical value (in a variable), and not a fix constant.

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