FSM-based Digital Design using Verilog HDL

4

Synchronous Finite-State Machine Designs

This chapter looks at a number of practical designs using the techniques developed in Chapters 1 to 3. It compares the conventional design of FSMs with the design proposed in the book. This illustrates how more effective the latter method is in developing a given design. The traditional method of designing FSMs is common in a lot of textbooks on digital design. It makes use of transition tables and can become cumbersome to use when dealing with designs having a large number of inputs. Even for designs having few inputs, the method used in Chapters 1–3 is quicker and easier to use.

Most designers involved in the development of FSMs make use of unused secondary state assignments to help reduce the flip-flop input and output equations. This practice is investigated with some interesting results.

The chapter covers a number of practical system designs. Some have simulation waveforms showing the FSM design working. The Verilog HDL code used to create the simulations will not be shown, as Verilog HDL code development is not covered until later on in the book. However, the respective Verilog codes are available on the CDROM disk that is included with this book, as are the Verilog tools used to view the simulations.

Eight examples are discussed in this chapter, with each example introducing techniques that help to solve the particular requirements in the design being investigated.

4.1 TRADITIONAL STATE DIAGRAM SYNTHESIS METHOD

Before continuing ...