Errors in VHDL

In VHDL, error handling is typically done through the use of assertions, report statements, and simulation control. Unlike Go, VHDL doesn’t have a built-in error type or return mechanism for functions. Instead, we’ll use a combination of these techniques to demonstrate error handling.

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

entity ErrorHandling is
end ErrorHandling;

architecture Behavioral of ErrorHandling is
    -- Function to demonstrate error handling
    function f(arg : integer) return integer is
    begin
        if arg = 42 then
            report "can't work with 42" severity error;
            return -1;
        end if;
        return arg + 3;
    end function;

    -- Procedure to demonstrate more complex error handling
    procedure make_tea(arg : in integer; success : out boolean) is
    begin
        success := true;
        if arg = 2 then
            report "no more tea available" severity warning;
            success := false;
        elsif arg = 4 then
            report "making tea: can't boil water" severity error;
            success := false;
        end if;
    end procedure;

begin
    process
        variable result : integer;
        variable tea_success : boolean;
    begin
        -- Demonstrating f function
        for i in 7 to 42 loop
            result := f(i);
            if result = -1 then
                report "f failed for input: " & integer'image(i);
            else
                report "f worked: " & integer'image(result);
            end if;
            exit when i = 42;
        end loop;

        -- Demonstrating make_tea procedure
        for i in 0 to 4 loop
            make_tea(i, tea_success);
            if not tea_success then
                if i = 2 then
                    report "We should buy new tea!";
                elsif i = 4 then
                    report "Now it is dark.";
                else
                    report "Unknown error in making tea";
                end if;
            else
                report "Tea is ready!";
            end if;
        end loop;

        wait;
    end process;
end Behavioral;

In this VHDL code:

We define a function f that returns an integer. If the input is 42, it reports an error and returns -1. Otherwise, it returns the input plus 3.
We define a procedure make_tea that takes an integer input and has a boolean output to indicate success. It reports different messages based on the input.
In the main process, we demonstrate the use of these error handling mechanisms:
- We loop through values and call the f function, reporting success or failure.
- We then demonstrate the make_tea procedure, handling different error conditions.
VHDL uses report statements for error messaging. The severity can be set to note, warning, error, or failure.
Instead of returning errors, we use out parameters (like success in make_tea) or specific return values (like -1 in f) to indicate errors.
VHDL doesn’t have built-in error chaining or wrapping. For more complex error handling, you would typically use custom record types or additional out parameters.

To run this VHDL code, you would typically use a VHDL simulator. The simulation would show the reported messages, which serve as our error indications.

This approach demonstrates error handling in VHDL, adapting the concepts from the original example to fit VHDL’s paradigms and best practices.

Range Over Iterators in VHDL

Custom Errors in VHDL

Learn X By Example

Title here

Errors in VHDL