24-02-2016, 02:51 PM
VHDL is a hardware description language for modeling digital circuits that can range from the simple connection of gates to complex systems. VHDL is an acronym for VHSIC Hardware Description Language, and VHSIC in turn is an acronym for Very High Speed Integrated Circuits. This appendix gives a brief summary of the basic VHDL elements and its syntax. Many advanced features of the language are omitted. Interested readers should refer to other references for detailed coverage.
VHDL identifier syntax:
• A sequence of one or more uppercase letters, lowercase letters, digits, and the underscore
• Upper and lowercase letters are treated the same (i.e., case insensitive)
• The first character must be a letter
• The last character cannot be the underscore
• Two underscores cannot be together