The Designer's Guide to VHDL, 3rd Edition

Appendix B. VHDL Syntax

In this appendix we present the full set of syntax rules for VHDL using the EBNF notation introduced in Chapter 1. The form of EBNF used in this book differs from that of the VHDL Language Reference Manual (LRM) in order to make the syntax rules more intelligible to the VHDL user. The LRM includes a separate syntax rule for each minor syntactic category. In this book, we condense the grammar into a smaller number of rules, each of which defines a larger part of the grammar. We introduce the EBNF symbols “(”, “)” and “...” as part of this simplification. Our aim is to avoid the large amount of searching required when using the LRM rules to resolve a question of grammar.

Those parts of the syntax rules that were introduced ...