Interfaces in VHDL

-- Interfaces are named collections of method signatures.
-- In VHDL, we can use records to define a structure similar to an interface.

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

entity Geometry is
end Geometry;

architecture Behavioral of Geometry is
    -- Define a record type for geometric shapes
    type geometry_record is record
        area : real;
        perim : real;
    end record;

    -- Define types for rect and circle
    type rect_record is record
        width : real;
        height : real;
    end record;

    type circle_record is record
        radius : real;
    end record;

    -- Function declarations
    function calc_rect_area(r : rect_record) return real;
    function calc_rect_perim(r : rect_record) return real;
    function calc_circle_area(c : circle_record) return real;
    function calc_circle_perim(c : circle_record) return real;
    procedure measure(g : geometry_record);

begin
    -- Main process
    process
        variable r : rect_record := (width => 3.0, height => 4.0);
        variable c : circle_record := (radius => 5.0);
        variable g : geometry_record;
    begin
        -- Calculate and measure rect
        g.area := calc_rect_area(r);
        g.perim := calc_rect_perim(r);
        measure(g);

        -- Calculate and measure circle
        g.area := calc_circle_area(c);
        g.perim := calc_circle_perim(c);
        measure(g);

        wait;
    end process;
end Behavioral;

-- Function implementations
function calc_rect_area(r : rect_record) return real is
begin
    return r.width * r.height;
end function;

function calc_rect_perim(r : rect_record) return real is
begin
    return 2.0 * r.width + 2.0 * r.height;
end function;

function calc_circle_area(c : circle_record) return real is
    constant PI : real := 3.14159265358979323846;
begin
    return PI * c.radius * c.radius;
end function;

function calc_circle_perim(c : circle_record) return real is
    constant PI : real := 3.14159265358979323846;
begin
    return 2.0 * PI * c.radius;
end function;

-- Procedure implementation
procedure measure(g : geometry_record) is
begin
    report "Area: " & real'image(g.area);
    report "Perimeter: " & real'image(g.perim);
end procedure;

In this VHDL translation, we’ve created a structure similar to interfaces using records. The geometry_record type serves as our “interface”, containing the area and perim fields.

We define separate record types for rect and circle, and implement functions to calculate their areas and perimeters. The measure procedure takes a geometry_record as an argument, which allows it to work with any shape that conforms to this structure.

In the main process, we create instances of rect and circle, calculate their properties, and then call the measure procedure for each.

Note that VHDL doesn’t have built-in object-oriented features like interfaces or methods, so we’ve adapted the concept using records and separate functions. The measure procedure demonstrates polymorphism by accepting a geometry_record, which can represent different shapes.

This VHDL code would typically be used in hardware design and simulation environments, rather than being compiled and run like a software program.

Methods in VHDL

Enums in VHDL

Learn X By Example

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Interfaces in VHDL