Table of Contents
What is difference between function and procedure in VHDL?
Both procedures and functions written in VHDL must have a body and may have declarations. Procedures perform sequential computations and return values in global objects or by storing values into formal parameters. Functions perform sequential computations and return a value as the value of the function.
What is procedure in VHDL?
A procedure is a type of subprogram in VHDL which can help us avoid repeating code. Sometimes the need arises to perform identical operations several places throughout the design. While creating a module might be overkill for minor operations, a procedure is often what you want.
How does function work in VHDL?
Functions are subprograms in VHDL which can be used for implementing frequently used algorithms. A function takes zero or more input values, and it always returns a value. In addition to the return value, what sets a function apart from a procedure, is that it cannot contain Wait-statements.
Are VHDL functions synthesizable?
Both function and procedure can be synthesizable, the main difference between them is that function returns only one signal but a procedure may return many, I used both function, procedure in behavioral and RTL code.
What is the difference between variable and signal in VHDL?
The main difference between signal and variable in VHDL is that a signal is an object with a past history of values, while a variable is an object with a single current value. The VHDL is a popular HDL, which stands for High-Level Description Language.
Can VHDL function return multiple values?
Functions are subprograms and can have multiple inputs or no input at all. However, a function in VHDL always returns a value.
What are the two sections in a VHDL file what are their functions?
A VHDL design consists of one or more entities. Entities have defined inputs and outputs and perform a defined function. Each design has two parts, an entity specification and an architecture. The entity specification defines the design’s inputs and outputs, and the architecture determines its function.
What is synthesizable and non-synthesizable?
For something to be synthesizable it has to be able to be represented in hardware, i.e. using logic gates. An example of something that is non-synthesizable would be initializing a design with values assigned to signals or registers. This cannot be translated to hardware, therefor is non-synthesizable.
What is the difference between procedural and functional programming?
Procedural programming uses a very detailed list of instructions to tell the computer what to do step by step. This approach uses iteration to repeat a series of steps as often as needed. Functional programming is an approach to problem solving that treats every computation as a mathematical function.
What is diff between stored procedure and function?
What are the differences between Stored procedures and functions?
| Functions | Procedures |
|---|---|
| You cannot call stored procedures from a function | You can call a function from a stored procedure. |
| You can call a function using a select statement. | You cannot call a procedure using select statements. |
What is the difference between concurrent and sequential statements in VHDL?
The primary concurrent statement in VHDL is a process statement. A number of processes may run at the same simulated time. Within a process, sequential statements specify the step-by-step behavior of the process, or, essentially, the behavior of an architecture.
Can you have two returns in a function?
No, you can not have two returns in a function, the first return will exit the function you will need to create an object.
What is the difference between an entity and architecture declaration?
The entity declaration provides the “external” view of the component; it describes what can be seen from the outside, including the component ports. The architecture body provides an “internal” view; it describes the behavior or the structure of the component.
What is a procedure in VHDL?
A procedure in VHDL is a subprogram. In VHDL there are 2 types of subprogram: Differences between procedures and functions are basically: Procedure can return more than one argument, can have input parameters, output parameters, and inout parameters.
What are the different types of subprograms in VHDL?
In VHDL there are 2 types of subprogram: Differences between procedures and functions are basically: Procedure can return more than one argument, can have input parameters, output parameters, and inout parameters. Function always returns just one.
Can VHDL be used as a programming language?
Even if the VHDL is a hardware description language, it can define procedures like a common programming language. When we use a procedure, we always need to take in mind how the procedure code is translated in hardware implementation.
How do I include a package in a VHDL design unit?
To include the package in a VHDL design unit, we must include the relevant library and package. The code snippet below shows the method we use to include a library and packe in our VHDL design.