Page 25 - DSP Integrated Circuits

10 Chapter 1 DSP Integrated Circuits

Yet another view is the architectural description that is used to describe how a
number of objects (components) are interconnected. An architectural description is
sometimes referred to as a structural description. In general, a structural descrip-
tion does not describe the functionality of the circuit, but it may include informa-
tion about actual or estimated performance. Thus, two systems exhibiting the
same behavior could be provided by different structures. Note that different struc-
tures exist at different levels of the design hierarchy and that behavioral and
structural descriptions may appear in the same view.

EXAMPLE 1.1

A behavioral description of an XNOR gate is

Propose two structural descriptions, or architectures, using different types of com-
ponents.
Figure 1.8 shows a structural descrip-
tion at the logic abstraction level of an XNOR
gate that uses behavioral descriptions of the
components: inverters, AND gates, and OR
gates. Figure 1.9 shows yet another struc-
tural description of an XNOR gate with tran-
sistors as basic components. Hence, several Figure 1.8 Structural description
different structures are possible. of an XNOR gate

Figure 1.9 Structural description of a CMOS XNOR gate

1.6 DSP SYSTEM DESIGN

For the things we have to learn before we can do them, we learn by doing.
—Aristotle
In the system design phase, a behavioral view of the system is mapped onto an
appropriate hardware structure by a sequence of mappings. The starting point for