The Designer's Guide to VHDL, 2nd Edition

2 Scalar Data Types and Operations

The concept of type is very important when describing data in a VHDL model. The type of a data object defines the set of values that the object can assume, as well as the set of operations that can be performed on those values. A scalar type consists of single, indivisible values. In this chapter we look at the basic scalar types provided by VHDL and see how they can be used to define data objects that model the internal state of a module.

2.1 Constants and Variables

An object is a named item in a VHDL model that has a value of a specified type. There are four classes of objects: constants, variables, signals and files. In this chapter, we look at constants and variables; signals are described fully in ...