VHDL is a language for describing digital hardware. This lesson introduces its purpose, origins, and standardization, then explains how its logic types developed.
VHDL stands for VHSIC Hardware Description Language; VHSIC means Very High Speed Integrated Circuits. Unlike a general-purpose programming language that primarily describes instructions for a processor, VHDL describes the behavior and structure of digital systems. A design can be expressed at several levels of abstraction, from a system-level description down to logic gates.
All flashcards
What is VHDL?
VHDL, or VHSIC Hardware Description Language, is a strongly typed, case-insensitive language for describing the behavior and structure of digital systems.
Why was VHDL originally developed?
It was developed to document ASIC behavior for the U.S. Department of Defense's VHSIC program; those descriptions later supported simulation and synthesis.
What does IEEE 1164 provide for VHDL?
It introduced nine-valued logic packages, including std_logic and std_logic_vector.
What does resolution do for a std_logic signal?
A resolution function determines the resulting value when multiple drivers assign to the signal.
What is VHDL-AMS?
An analog and mixed-signal extension associated with IEEE 1076.1.
Quiz questions
What does synthesis do with a suitable VHDL description?Answer: Maps synthesizable descriptions into gates and wires for a target device.
How does a transparent latch differ from a D-type flip-flop?Answer: A latch can update while enabled; a flip-flop samples input at a clock edge.
In event-driven VHDL simulation, where are signal updates scheduled?Answer: In an event queue associated with simulation times.
What does a VHDL testbench do?Answer: Applies input stimuli and observes or checks a design's behavior in simulation.
What does VHDL concurrency allow a design to express?Answer: Multiple hardware activities occurring during the same interval.
Based on the Wikipedia article VHDL, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.