The Designer's Guide to VHDL

Peter J. Ashenden


by Paul Menchini, Research Triangle Park, North Carolina

Digital electronic systems are increasing exponentially in their complexity over time. This fact, coupled with decreasing product lifetimes and increasing reliability requirements, has forced designers to dramatically increase their productivity and the quality of their designs.

VHDL was developed in response to these trends. Borrowing complexity management and error detection techniques from the software engineering world, VHDL was developed to eliminate irrelevant detail, allow technology-independent description, catch errors earlier, and promote portable and interoperable models from the gate to the system level.

In response, EDA tools have been designed to take an ever-greater share of the burden from designers. A single representation medium can now drive design processes from specification down to detailed digital design.

Originally developed as the United States Department of Defense's standard hardware description language (HDL), VHDL has evolved through two additional rounds of IEEE standardization into one of the two preeminent HDLs in use throughout the world. Continued development in the areas of detailed timing models, synthesis directives, analog capabilities, and so forth mean the VHDL will continue to provide the expressive facilities needed by state-of-the-art designs well into the next century. New tools leveraging on VHDL's precise definition continue to be introduced and offer increased simulation performance, increased synthesis capabilities, and entirely new capabiliites, such as the formal verification of the functional equivalence of models.

Because VHDL uses concepts not commonly found in hardware description, designers approaching VHDL for the first time need a sure guide to the features using these concepts. One of the few books on VHDL that does not rely heavily on experience with programming languages, A Designer's Guide to VHDL is ideal for the nonprogrammer wishing to learn VHDL.

This book explores in detail the latest version of VHDL, VHDL-93 (IEEE Std. 1076-1993). Assuming no prior knowledge of VHDL, Professor Ashenden walks the reader through VHDL, first addressing simple modeling issues, then moving on to the more complex. As VHDL contains many features, the reader is greatly aided by the inclusion of four fully worked case studies. These case studies put VHDL's features in context and show how they work in concert to model digital systems of varying levels of complexity and varying levels of detail.

Appendices cover the use of VHDL in synthesis, as well as other standards built upon the VHDL framework. As an aid to the experienced user of VHDL, other appendices contain syntax summaries and a list of differences from the initial IEEE standard, IEEE Std. 1076-1987.

Welcome to VHDL!