TABLE OF CONTENTS VHDL is a hardware description language. It describes the behavior of an electronic circuit or system, from which the physical circuit or system can then be attained (implemented).
VHDL stands for VHSIC Hardware Description Language. VHSIC is itself an abbreviation for Very High Speed Integrated Circuits, an initiative funded by the United States Department of Defense in the 1980s that led to the creation of VHDL. Its first version was VHDL 87, later upgraded to the so-called VHDL 93. VHDL was the original and first hardware description language to be standardized by the Institute of Electrical and Electronics Engineers, through the IEEE 1076 standard. An additional standard, the IEEE 1164, was later added to introduce a multi-valued logic system.
VHDL is intended for circuit synthesis as well as circuit simulation. However, though VHDL is fully simulatable, not all constructs are synthesizable. We will give emphasis to those that are.
A fundamental motivation to use VHDL (or its competitor, Verilog) is that VHDL is a standard, technology/vendor independent language, and is therefore portable and reusable. The two main immediate applications of VHDL are in the field of Programmable Logic Devices (including CPLDs Complex Programmable Logic Devices and FPGAs Field Programmable Gate Arrays) and in the field of ASICs (Application Specific Integrated Circuits). Once the VHDL code has been written, it can be used either to implement the circuit in a programmable device (from Altera, Xilinx, Atmel, etc.) or can be submitted to a foundry for fabrication of...
