10327: can't determine definition of operator ""=""

Discussion in 'VHDL' started by artvandelay, Mar 17, 2010.

  1. artvandelay

    artvandelay

    Joined:
    Nov 6, 2009
    Messages:
    3
    Hello!

    As the titles describes I get this error when trying to compile:
    Error (10327): VHDL error at ps2lab1.vhd(126): can't determine definition of operator ""="" -- found 0 possible definitions

    I have defined at the top of my code:

    library IEEE;
    use IEEE.STD_LOGIC_1164.ALL;
    use IEEE.STD_LOGIC_ARITH.ALL;
    use IEEE.STD_LOGIC_UNSIGNED.ALL;

    this is the part with the error:

    PROCESS (scan_ready)
    BEGIN
    IF (scan_ready'EVENT AND scan_ready = '1') THEN
    history(4) <= history(3);
    history(3) <= history(2);
    history(2) <= history(1);
    history(1) <= scan_code;
    END IF;
    END PROCESS;

    I don't understand why this won't work. Any idea?
    artvandelay, Mar 17, 2010
    #1
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  2. artvandelay

    jeppe

    Joined:
    Mar 10, 2008
    Messages:
    348
    Location:
    Denmark
    Which type used for the signal "scan_ready" ?
    jeppe, Mar 17, 2010
    #2
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  3. artvandelay

    artvandelay

    Joined:
    Nov 6, 2009
    Messages:
    3
    boolean signal for scan_ready
    artvandelay, Mar 17, 2010
    #3
  4. artvandelay

    joris

    Joined:
    Jan 29, 2009
    Messages:
    152
    If it is a boolean, you should not compare to '1'; you can use it without an explicit comparison:
    Code:
    PROCESS (scan_ready)
    BEGIN
    IF (scan_ready'EVENT AND scan_ready) THEN
    --code
    END IF;
    END PROCESS;
    
    Or, if you prefer, you can explicitly compare to true:
    Code:
    PROCESS (scan_ready)
    BEGIN
    IF (scan_ready'EVENT AND scan_ready = true) THEN
    --code
    END IF;
    END PROCESS;
    
    joris, Mar 17, 2010
    #4
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