-------------------------------------------------------------------------------
-- Copyright (c) 2003 Mentor Graphics Corporation
--
-- This model is a component of the Mentor Graphics VHDL-AMS educational open 
-- source model library, and is covered by this license agreement. This model,
-- including any updates, modifications, revisions, copies, and documentation 
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-------------------------------------------------------------------------------
-- File       : vco_digital_out.vhd
-- Author     : Mentor Graphics
-- Created    : 2003-05-30
-- Last update: 
-------------------------------------------------------------------------------
-- Description: Voltage Controlled Oscillator (VCO) with digital output state.
-------------------------------------------------------------------------------
-- Revisions  :
-- Date        Version     Author              Description
-- 2003-05-30  1.0         Mentor Graphics     Created
-------------------------------------------------------------------------------

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.electrical_systems.all;

entity vco_digital_out is
  generic (fmax   : real := 2.7e9;    -- Frequency when v_input = vmax
		   fmin   : real := 2.3e9;    -- Frequency when v_input = vmin
           vmax   : real := 1.0;      -- Input voltage for fmax
		   vmin   : real := -1.0);    -- Input voltage for fmin

  port (d_out        : out std_logic;        -- Digital output
        terminal v_input :    electrical);   -- Input control (voltage)

end entity vco_digital_out;

architecture behavioral of vco_digital_out is
  quantity period : real;
  quantity v across v_input to electrical_ref;
  constant gain : real := (fmax - fmin)/(vmax - vmin);
begin

  CreateEvent : process
  begin
    d_out <= '0';
    wait until domain = time_domain;
	loop
      d_out <= '0';
      wait for period/2.0;
      d_out <= '1';
      wait for period/2.0;
    end loop;
  end process CreateEvent;

  period == 1.0/((v - vmin)*gain + fmin);

end architecture behavioral;

-------------------------------------------------------------------------------
-- Copyright (c) 2003 Mentor Graphics Corporation
-------------------------------------------------------------------------------