VHDL Programming

boolean expression construct to describe the syntax required, none will be

found. The reason is that all expressions share the same syntax description.

For our purposes, the boolean type of the expression is ignored, and the

construct description can be found under the following description:

expression ::=

relation {and relation}

|relation {or relation}

|relation {xor relation}

| relation [nand relation]

|relation [nor relation]

To summarize, curly braces { }are optional and repeatable constructs,

square brackets [ ]are optional constructs, and italic pieces of a con-

struct can be ignored for purposes of finding descriptions.

Appendix C: Reading VHDL BNF 447