Custom Errors in VHDL

Our custom error example demonstrates how to create and use custom error types in VHDL. While VHDL doesn’t have built-in error handling mechanisms like some high-level programming languages, we can simulate a similar concept using records and functions.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity CustomError is
end CustomError;

architecture Behavioral of CustomError is
    -- Define a custom error type
    type ArgError is record
        arg     : integer;
        message : string(1 to 20);
    end record;

    -- Function to create an ArgError
    function CreateArgError(arg : integer; message : string) return ArgError is
        variable err : ArgError;
    begin
        err.arg := arg;
        err.message := (others => ' ');  -- Initialize with spaces
        err.message(1 to message'length) := message;
        return err;
    end function;

    -- Function to simulate error handling
    function f(arg : integer) return ArgError is
    begin
        if arg = 42 then
            return CreateArgError(arg, "can't work with it");
        else
            return CreateArgError(0, "");  -- No error
        end if;
    end function;

    -- Procedure to print ArgError
    procedure PrintArgError(err : ArgError) is
    begin
        if err.arg /= 0 then
            report "Error: " & integer'image(err.arg) & " - " & err.message;
        end if;
    end procedure;

begin
    process
        variable result : ArgError;
    begin
        -- Test the function
        result := f(42);
        PrintArgError(result);
        
        result := f(10);
        PrintArgError(result);
        
        wait;
    end process;
end Behavioral;

In this VHDL example, we’ve created a custom error type called ArgError using a record. The CreateArgError function is used to create instances of this custom error type.

The f function simulates a function that might return an error. If the input argument is 42, it returns a custom error; otherwise, it returns a “no error” state.

The PrintArgError procedure is used to display the error message if an error occurred.

In the main process, we test the f function with different inputs and print the results.

To run this VHDL code, you would typically use a VHDL simulator such as ModelSim or GHDL. The simulation would produce output similar to:

# Error: 42 - can't work with it

This example demonstrates how to implement a basic error handling mechanism in VHDL using custom types and functions. While it’s not as sophisticated as error handling in high-level languages, it provides a way to pass and check for error conditions in VHDL designs.

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Custom Errors in VHDL