This book is intended to be a working reference for electronic hardware de- signers who are interested in writing VHDL models. A handbook/cookbook approach is taken, with many complete examples used to illustrate the fea- tures of the VHDL language and to provide insight into how particular classes of hardware devices can be modelled in VHDL. It is possible to use these models directly or to adapt them to similar problems with minimal effort. This book is not intended to be a complete reference manual for the VHDL language. It is possible to begin writing VHDL models with little background in VHDL by copying examples from the book and adapting them to particular problems. Some exposure to the VHDL language prior to using this book is recommended. The reader is assumed to have a solid hardware design background, preferably with some simulation experience. For the reader who is interested in getting a complete overview of the VHDL language, the following publications are recommended reading: - An Introduction to VHDL: Hardware Description and Design LIP89] - IEEE Standard VHDL Language Reference Manual IEEE87] - Chip-Level Behavioral Modelling ARMS88] - Multi-Level Simulation of VLSI Systems COEL87] Other references of interest are USG88], DOD88] and CLSI87] Use of the Book If the reader is familiar with VHDL, the models described in chapters 3 through 7 can be applied directly to design problems.