vhdl

Procedure call through different packages in VHDL

Let's say I have two packages : package_1 and package_2 and an entity : my_entity.

The entity uses the first package

-- This is my_entity
USE WORK.package_1.ALL;

The package_1 uses the second package;

-- This is package_1
USE WORK.package_2.ALL;

The package_2 implements a procedure called ... my_procedure (y)

-- This is package_2
PROCEDURE my_procedure IS ...

Now, is there a way to call my_procedure from my_entity? The current version isn't compiling in Modelsim.

Solution

  • Your entity also requires a reference to:

    USE WORK.package_2.ALL;

    In VHDL, a package reference is to a compiled image that is in the library and only gets what is in the corresponding declarative part of the package. IE: unlike C, it does not get anything from the packages that are referenced by a package.

    This is good as it helps isolate declarations - only include what you need and that is all that you get.

    From note of @user1818839, you can just make my_procedure visible by doing:

    USE work.package_2.my_procedure;

    Alternately, if you want access to my_procedure when referencing package_1, then an alias will work well:

    alias my_procedure is work.package_2.my_procedure[TypeOfParam1];

    For an example of this, see the VHDL-2008 version of std_logic_textio which aliases to std_logic_1164 (without ambiguity since they are the same procedure).