時序電路設(shè)計實例 (Sequential-Circuit Design Examples):We noted in previous chapters that we typically deal with digital
systems in smaller chunks, for example, partitioning them into data paths,
registers, and control units (Section 8.7.1). In fact, a typical system has
multiple functional units with well defined interfaces and connections
between them (as supported by VHDL, Section 4.7.2), and each functional
unit may contain a hierarchy with several layers of abstraction (as supported
by both VHDL and typical schematic drawing packages [Section 5.1.6]).
Thus, we can deal with sequential circuits in much smaller chunks.
After all of this build-up, I have to admit that the design of complex,
hierarchical digital systems is beyond the scope of this text. However, the
heart of any system or any of its subsystems is typically a state machine or
other sequential circuit, and that’s something we can study here. So, this
chapter will try to reinforce your understanding of sequential circuit and state-machine design presenting several examples.