Configuring a 2's compliment

Engineering 🇬🇧
vvora
2021-11-29
2021-12-05

  • vvora - 2021-11-29

    Hi,

    I have an array of Bytes reading different messages from a COB-ID, one of them is a 16 bit signed INT, 2's compliment and other one is 16 bit unsigned INT, 2's compliment. What would be the best way to read them. Any function block for conversion? I assume I will have to take 2's compliment of the data read?

    Thanks

     

  • TimvH

    TimvH - 2021-12-05

    Possible solution is to define a DUT Type Union with Array of 2 bytes and an int:

    TYPE U_2B_I :
UNION
    ab : ARRAY[0..1] OF BYTE;
    i : INT;
END_UNION
END_TYPE

    Then declare a variable of this type in your application, write the 2 bytes into the array and use the int

    VAR
    u1 : U_2B_I;
    iResult: INT;
END_VAR

u1.ab[0] := 2#0000_0000;
u1.ab[1] := 2#1000_0000;
iResult := u1.i;
     

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