VHDL - Hardware description language

VHDL, aka VHSIC Hardware Description Language, is a hardware description language created in 1983.

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VHDL (VHSIC Hardware Description Language) is a hardware description language used in electronic design automation to describe digital and mixed-signal systems such as field-programmable gate arrays and integrated circuits. VHDL can also be used as a general purpose parallel programming language.. Read more on Wikipedia...

Tags: hardwareDescriptionLanguage
There are at least 34,211 VHDL repos on GitHub
The Google BigQuery Public Dataset GitHub snapshot shows 2k users using VHDL in 2k repos on GitHub
There are 2,320 members in the VHDL subreddit
Explore VHDL snippets on Rosetta Code
VHDL on HOPL
VHDL ranks #44 in the TIOBE Index
ANTLR grammar for VHDL
VHDL LSP implementation
CodeMirror package for syntax highlighting VHDL
Pygments supports syntax highlighting for VHDL
GitHub supports syntax highlighting for VHDL
See also: (6 related languages) Verilog, Ada, Pascal, VHDL-AMS, Property Specification Language, ISBN
5 PLDB concepts link to VHDL: Ace Editor, invokator, mal, Pygments, Spatial

Example from hello-world:

use std.textio.all;

entity hello_world is
end hello_world;

architecture behaviour of hello_world is
begin
	process
    begin
       write (output, String'("Hello World"));
       wait;
    end process;
end behaviour;

Example from the Hello World Collection:

--Hello World in VHDL

ENTITY helloworld IS
END helloworld;

ARCHITECTURE hw OF helloworld IS

BEGIN

ASSERT FALSE
REPORT "HELLO, WORLD!"
SEVERITY NOTE;

END hw;

Example from Linguist:

-- VHDL example file

library ieee;
use ieee.std_logic_1164.all;

entity inverter is
	port(a : in std_logic;
	     b : out std_logic);
end entity;

architecture rtl of inverter is
begin
	b <= not a;
end architecture;

Example from Wikipedia:

process
begin
  wait until START = '1'; -- wait until START is high
  
  for i in 1 to 10 loop -- then wait for a few clock periods...
    wait until rising_edge(CLK);
  end loop;

  for i in 1 to 10 loop 	-- write numbers 1 to 10 to DATA, 1 every cycle
    DATA <= to_unsigned(i, 8);
    wait until rising_edge(CLK);
  end loop;

  -- wait until the output changes
  wait on RESULT;
  
  -- now raise ACK for clock period
  ACK <= '1';
  wait until rising_edge(CLK);
  ACK <= '0';

  -- and so on...
end process;

VHDL Keywords

abs access after alias all and architecture array assert attribute begin block body buffer bus case component configuration constant disconnect downto else elsif end entity exit file for function generate generic group guarded if impure in inertial inout is label library linkage literal loop map mod nand new next nor not null of on open or others out package port postponed procedure process pure range record register reject rem report return rol ror select severity signal shared sla sll sra srl subtype then to transport type unaffected units until use variable wait when while with xnor xor

Language features

Feature	Supported	Example	Token
Binary Literals	✓	-- B"[01_]+"
Integers	✓	-- \d{1,2}#[0-9a-f_]+#?
Floats	✓	-- (\d+\.\d*\|\.\d+\|\d+)E[+-]?\d+
Hexadecimals	✓	-- X"[0-9a-f_]+"
Octals	✓	-- O"[0-7_]+"
Conditionals	✓
Functions	✓
While Loops	✓
Strings	✓	"Hello world"	"
Case Insensitive Identifiers	✓	signals some_signal : integer ; signal some_other_signal : integer ; signal result : integer ; ReSULT <= SOME_SIGNAL + sOME_oTHer_SIGNal ; -- Although totally unrecommended - this is perfectly legal
Print() Debugging	✓		write
Line Comments	✓	-- A comment	--
Comments	✓
Semantic Indentation	X
MultiLine Comments	X