Currently, I specify the matrix dimensions in the vhdl code and use the corresponding type from the package. In this section, package body is discussed using Listing 6.4 and Listing 6.5.

in one file, instead of declaring in each file as shown in A procedure contains a list of input and outputs arguments, and defined in declaration part of the architecture as shown in lines 19-25 of ‘Functions’ are similar to ‘procedures’ but can have input-ports only and return only one value. This makes it more convenient to write flexible, re-usable code. port names and constants values etc. In the component instantiation, the generic map statement can map the new values in the component. In the entity declaration, all the values that have to be customized can be passed using generic clause. The matrix dimensions have been defined in a package. In order to implement parameterization of an entity VHDL introduce the generic clause. 6.4. Similarly, signal ‘f’ used in line 38 which is also defined in the package.
A package file is often (but not always) used in conjunction with a unique VHDL library. Note that, ‘work’ is the default directory where all the compiled file are stored.Next, line 30 adds two number, in which ‘S’ is defined in the package.Line 33 is using the procedure ‘sum2Num’ which is declared in the package. Rest of the working of line 38-55 is same as In this chapter, we discuss the procedure and package. Sunday, Sep 24th, 2017. All these declarations are used by -- procedure for adding two numbers i.e. VHDL-2008 adds package generics, which can be used to parameterize a package and the ability to declare packages locally in the declaration region of a process, subprogram, protected body type, or another package. Procedures are used to define common operations within many designs. A generic package is declared by adding a generic statement to the package.

Explanation Listing 6.4

VHDL allows the designer to parametrize the entity during the component instantiation.The RAMs are similar. In line 19, ‘sum2Num’ is the name of the procedure, which has two input signal (a and b) and two output signals (sum and diff). Further, procedure is declared in the package (line 12-19), and then defined in the package body (line 24-29). Have the same interface in terms of signal but In the entity declaration, all the values that have to be customized can be passed using You should notice that in the entity declaration the generic parameters can have a default values.The default value is not mandatory. Packages¶ Note that the functions and the procedures can be defined in declaration parts of the entities and architectures; but the best place for defining these are in the packages. The working of this part is same as Line 26 defines the signal ‘currentState’ of type ‘stateType’ which is declared in package. In VHDL, generics have always been allowed on entities.

Standard VHDL Packages VHDL standard packages and types The following packages should be installed along with the VHDL compiler and simulator. This enables you to write parameterized design entities, such as an N-bit counter. © Copyright 2017, Meher Krishna Patel. A package in VHDL is a collection of functions, procedures, shared variables, constants, files, aliases, types, subtypes, attributes, and components. In this chapter, procedure and packages are discussed. Note that signal ‘p’ is mapped to ‘sum’ signal, therefore line 28 is used to assign the value of ‘p’ to output port ‘d’. How to use Constants and Generic Map in VHDL. Creating modules is a great way to reuse code, but often you need the same module with smaller variations throughout your design. The packages are already discussed in Section 2. The packages are already discussed in In this listing, line 6 adds all the declaration of ‘myPackage’ to current design. Then, line 27 maps the input and output port of the entity to this procedure. In this case (RAM2 instance) if no generic mapping is performed, the default values are applied in the current component instantiation.

VHDL-2008 allows generics on packages and subprograms too. It allows you to make certain parts of the module configurable at compile-time. Note that, a ‘return’ statement is required in the functions as shown in Lines 23 and 21 of Differences between the function and the procedure blocks,Note that the functions and the procedures can be defined in declaration parts of the entities and architectures; but the best place for defining these are in the packages. Further, packages are used to define common declarations i.e. However, I would like to use generic in the design to deal with matrices of different dimensions. For this I would have to somehow use the right type defined in the package. In the listing constants (line 9), signals (line 17), data-types (line 18) and procedure (line 12) are defined inside the package ‘myPackage’. We define some of the previous designs in the package, and then use the package to create new design. For an example, see the synthesizable fixed and floating point packages below. This is what generics and the generic map is for. num1 + num2 Packages are most often used …