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How to define package in VHDL?
A package in VHDL is a collection of functions, procedures, shared variables, constants, files, aliases, types, subtypes, attributes, and components. A package file is often (but not always) used in conjunction with a unique VHDL library.
What is alias in VHDL?
An alias is an alternative name for an existing object (signal, variable or constant). Such “alias” signals should be assigned concurrently, and “alias” variables should be reassigned each time their process is activated. Whats New in ’93. Aliases may be applied much more extensively in VHDL-93.
What is package body in VHDL?
The package body includes complete definitions of subprogram body declarations as well as values of deferred constants declared in corresponding package declarations. Other declarations (similar to those of package declaration) are also allowed here, but are visible only inside the package body.
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. A procedure doesn’t return a value like a function does, but you can return values by declaring out or inout signals in the parameter list.
What is the use of generic in VHDL?
In VHDL, generics are a local form of constant which can be assigned a value when we instantiate a component. As generics have a limited scope, we can call the same VHDL component multiple times and assign different values to the generic. We can use generics to configure the behaviour of a component on the fly.
What is alias in SV?
It is a way of providing a more user friendly name for another signal, or a select of another signal. The alias construct provides one other feature that is to connect two different nets together without knowing the direction of data flow. That avoids extraneous buffers or assign statements.
What is type in VHDL?
VHDL is a strongly typed language. Every constant, signal, variable, function, and parameter is declared with a type, such as BOOLEAN or INTEGER, and can hold or return only a value of that type. VHDL predefines abstract data types, such as BOOLEAN, which. are part of most programming languages, and hardware-re-
What are generic methods?
Generic methods are methods that introduce their own type parameters. This is similar to declaring a generic type, but the type parameter’s scope is limited to the method where it is declared. Static and non-static generic methods are allowed, as well as generic class constructors.
What is the purpose of the VHDL alias syntax?
The intended use is for design verification, allowing a testbench to reach objects not visible at the top level of a design. See Peter Ashenden and Jim Lewis The Designer’s Guide to VHDL (3rd Ed.), Section 18.1 External Names and Doulos VHDL-2008: Easier to use, Hierarchical Names, or IEEE Std 1076-2008, 8.7 External names.
Where do declarations go in a VHDL file?
Synthesisable declarations and non-synthesisable declarations (e.g.for a test bench) should therefore be placed in separated packages. Design Libraries are often not supported, so design files containing packages must either by analysed first for synthesis, or be present in the local directory.
Where does the package go in vhdl-93?
If a package has a body, it must usually be in the same design file as the package itself. In VHDL -93, the keyword end may be followed by the keyword package, for clarity and consistancy.
How are procedures and functions used in VHDL?
Just like functions, we use procedures to implement small sections of code which we can reuse throughout our code. In VHDL, a procedure can have any number of inputs and can generate multiple outputs. Unlike functions, we can also use constructs which consume time in a procedure.