Asynchronous Circuit Design

3

Communication Protocols

(The Chief Programmer) needs great talent, ten years experience and considerable systems and applications knowledge, whether in applied mathematics, business data handling, or whatever.

—Fred P. Brooks, The Mythical Man Month

Never put off until run time what you can do at compile time.

—David Gries

In the beginning was the word. But by the time the second word was added to it, there was trouble. For with it came syntax ….

—John Simon

In this chapter we describe the handshake protocols that are used to implement channel communication and methods of translation from a channel-level specification to a protocol-level description.

3.1 BASIC STRUCTURE

As we saw in Chapter 1, a channel communication can be implemented through a handshake protocol on two or more signal wires. One or more wires are used to request the communication; the others are used to acknowledge completion of the communication. In this section we describe how handshake protocols can be described in VHDL. Throughout the rest of the chapter, we use similar language constructs to describe alternative protocols. One of the alternative protocols from this chapter is given below. This protocol is for a passive/active shop which communicates one bit of data (i.e., one of two different types of wine) using a dual-rail protocol. In this section we describe the basic structure and syntax. The behavior and rationale of this and alternative protocols are described in future sections.

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