Page 271 - The Mechatronics Handbook

Product
Requirements

Product
Specifications

Design

A
Simulation

Implementation

B Testing

FIGURE 13.1 Product design process. A: mature technology, B: immature technology.

An important aspect of this infrastructure is that it also provides, at relatively low cost, access to
example devices and systems, made with stable fabrication processes, whose behavior can be tested
and compared to simulation results, thereby enabling improvements in simulation techniques.
• “Levels and views” (abstraction and encapsulation or “information hiding”) (see [9]). This concept
is illustrated in Fig. 13.2(a). For the VLSI domain, we can identify at least five useful levels of
abstraction, from the lowest (layout geometry) to the highest (system specification). We can also
“view” a system behaviorally, structurally, or physically. In the behavioral domain we describe the
functionality of the circuit without specifying how this functionality will be achieved. This allows us
to think clearly about what the system needs to do, what inputs are needed, and what outputs will
be provided. Thus we can view the component as a “black box” that has specified responses to given
inputs. The current through a MOS field effect transistor (MOSFET), given as a function of the
gate voltage, is a (low-level) behavioral description, for example. In the physical domain we specify
the actual physical parts of the circuit. At the lowest levels in this domain, we must choose what
material each piece of the circuit will be made from (for example, which pieces of wire will lie in
each of the metal layers usually provided in a CMOS circuit) and exactly where each piece will be
placed in the actual physical layout. The physical description will be translated directly into mask
layouts for the circuit. The structural domain is intermediate between physical and behavioral. It
provides an interface between the functionality specified in the behavioral domain, which ignores
geometry, and the geometry specified in the physical domain, which ignores functionality. In this
intermediate domain, we can carry out logic optimization and state minimization, for example.

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