Verilog

It was originally a language proprietary to Cadence Design Systems (http://www.cadence.com/) for use with their logic simulators[?], but the increasing success of VHDL prompted Cadence to move down the Open Standards[?] route, and Verilog is now IEEE Standard 1364.

Verilog has a syntax reminiscent of C, which helps explain its rapid take up among engineers who had already learnt to use that language. It is case-sensitive.

An example counter circuit follows:

module Div20x (rst, clk, cet, cep, count,tc);
//TITLE   'Divide-by-20 Counter with enables'

//enable CEP is a clock enable only
//enable CET is a clock enable and enables the TC output

//a counter using the Verilog language

    parameter size = 5;
    parameter length = 20;

    input rst;
    input clk;
    input cet;
    input cep;

    output [size-1:0] count;
    output tc;

    reg [size-1:0] count;
    wire tc;

    always @ (posedge rst or posedge clk)
        begin
            if (rst)
                count = 5'b0;
            else if (cet && cep)
            begin
                if (count == length-1)
                begin
                    count = 5'b0;
                end
                else
                    count = count + 1;
            end
        end

        assign tc = (cet && (count == length-1));

endmodule