-- Copyright (C) 2000-2002 The University of Cincinnati.  
-- All rights reserved. 

-- This file is part of VESTs (Vhdl tESTs).

-- UC MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
-- SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
-- IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
-- OR NON-INFRINGEMENT.  UC SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY
-- LICENSEE AS A RESULT OF USING, RESULT OF USING, MODIFYING OR
-- DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.

-- By using or copying this Software, Licensee agrees to abide by the
-- intellectual property laws, and all other applicable laws of the U.S.,
-- and the terms of this license.

-- You may modify, distribute, and use the software contained in this
-- package under the terms of the "GNU GENERAL PUBLIC LICENSE" version 2,
-- June 1991. A copy of this license agreement can be found in the file
-- "COPYING", distributed with this archive.

-- You should have received a copy of the GNU General Public License
-- along with VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 

-- ---------------------------------------------------------------------
--
-- $Id: inverter.ams,v 1.1 2002-03-27 22:11:18 paw Exp $
-- $Revision: 1.1 $
--
-- ---------------------------------------------------------------------

-- /**************************************************************************/
-- /* File: inverter.ams                                                     */
-- /**************************************************************************/
-- /* Author(s):        Vishwashanth Kasula Reddy & Venkateswaran Krishna    */
-- /* Date of creation: Mon Nov 30th 1998                                    */
-- /**************************************************************************/
--Roadmap:
----------
--This is a mixed signal model of an inverter... The input is a bit signal
-- which is converted to a 5/0 value realSignal. This signal is then given
-- to the input of the cmos inverter and the output of the cmos inverter is
-- then given to a atod... the final output is then a bit signal which is
-- the inverse of the input bit signal...

------------------------------------------------------------------------
--                             /\ Vdd
--                              | 
--                              o S
--                              |
--                             --
--                     -----<-|p
--                     |       --
--                     |        |
--          --0--/\/\--0      D 0--------o--------o----------
--         + /\        |        |        |        |        /\ +
--            |        |       --        >        |         |
--  vin is    |        ----->-|n         <       ---       Vout ==> atod ==> op
-- atod(inp)  Vin              --        >       ---        |
--            |                 |        <        |         |
--            |                 o S      |        |         |
--         - \/                 |        |        |        \/ -
--          -------------------------------------------------
--                                       |
--                                      ---
--                                       -
------------------------------------------------------------------------

-------*****************************************************************
--                   Package definition Begins 
-------*****************************************************************

PACKAGE electricalSystem IS
    NATURE electrical IS real ACROSS real THROUGH;
    FUNCTION SIN(X : real) RETURN real;
    FUNCTION EXP(X : real) RETURN real;
    FUNCTION SQRT(X : real) RETURN real;
    FUNCTION POW(X,Y : real) RETURN real;
--    ALIAS GND is electrical'reference;
END PACKAGE electricalSystem;

------- Square wave generator

-------*****************************************************************
--                   New Entity Begins : 1 BIT A/D CONVERTER
-------*****************************************************************

use work.electricalsystem.all;

entity a2d1bit is
	generic (vlo : real := 0.0;
	        vhi : real := 10.0;
	        ped : time := 1 ns);
	port (signal input : in bit;
	      terminal pos, neg : electrical);
end entity a2d1bit;

architecture behav of a2d1bit is
  quantity vsqr across isqr through pos to neg;
  signal vsig : real := 0.0;
begin

  vsqr == vsig;
  break on vsig;

  bit2real : process
  begin
    if(input = '0') then
      vsig <= vlo;
    else
      vsig <= vhi;
    end if;
    wait on input;
  end process; --- generator;

end architecture behav; 

-------*****************************************************************
--                   New Entity Begins : RESISTOR       
-------*****************************************************************
use work.electricalSystem.all;

entity resistor is
   generic(r: real := 1.0 );  --- resistance
   port( terminal tr1,tr2 : electrical); --- interface ports
end resistor;

architecture rbehavior of resistor is
   quantity Vr across Ir through tr1 to tr2;
begin
   Vr == Ir*r;
end architecture rbehavior; --- of resistor

-------*****************************************************************
--                   New Entity Begins : PMOS TRANSISTOR
-------*****************************************************************

----- PMOS 
--use std.textio.all;
use work.electricalsystem.all;

entity pmos is
    port (terminal g,s,d : electrical);
end entity pmos;

architecture behav of pmos is
  terminal g2, d1 : electrical;
  quantity vdsg across idsgi through d1 to s;
  quantity idsg through d1 to s;
  quantity vdsr across idsr through d1 to d;
  quantity vds across d to s;
  quantity vgs_in across g to s;
  quantity vgsr across igsr through g to g2;
  quantity vgs across igs through g2 to s;
  constant vth : real := 0.5;
  constant hfe : real := 3.54e-03;
--  quantity flag : real := 1.0; 
--    quantity vgs : real;
--  signal vgs_sig,vds_sig : real := 0.0;

begin
  ------ Setting initial conditions
--  init : break vds => 1.0;

  opn : vdsg == 1.0e+06 * idsgi ; -- almost 
  d12_res : vdsr == idsr * 1.0;
  g12res : vgsr == igsr * 1.0;
  g_oup : vgs == igs * 1.0;
  
--  flag == 1.0;
 
---- Current is in Micro Amps.

  ------ Cut OffRegion
    if((vgs <= 0.0) and (vgs >= vth)) use
	gnc :    idsg == 0.0;

  ------ Linear Region
  elsif((vds >= (vgs-vth)) and (vds < 0.0)) use
      	gnl :    idsg == -1.0*hfe*(((vgs-vth)*vds) - (pow(vds,2.0)/2.0));
 
  ------ Saturation Region
  elsif((vds < (vgs-vth)) and (vgs < vth)) use
      gns2 : idsg == -1.0*(hfe/2.0)*(pow((vgs-vth),2.0));

  ------ Other conditions
 -- elsif(vgs < 0.0 or vds <= 0.0) use
  elsif(1.0 = 1.0) use
      temp : idsg == 0.0;
  end use;

end architecture behav; --- of pmos;


-------*****************************************************************
--                   New Entity Begins : NMOS TRANSISTOR
-------*****************************************************************

----- NMOS 
--use std.textio.all;
use work.electricalsystem.all;

entity nmos is
    port (terminal g,s,d : electrical);
end entity nmos;

architecture behav of nmos is
  terminal g2, d1 : electrical;
  quantity vdsg across idsgi through d1 to s;
  quantity idsg through d1 to s;
  quantity vdsr across idsr through d1 to d;
  quantity vds across d to s;
  quantity vgs_in across g to s;
  quantity vgsr across igsr through g to g2;
  quantity vgs across igs through g2 to s;
  constant vth : real := 0.5;
  constant hfe : real := 8.85e-03;
--  quantity flag : real := 1.0; 
--    quantity vgs : real;
--  signal vgs_sig,vds_sig : real := 0.0;

begin
  ------ Setting initial conditions
--  init : break vds => 1.0;

  opn : vdsg == 1.0* idsgi ; -- almost 
  d12_res : vdsr == idsr * 1.0e-3;
  g12res : vgsr == igsr * 1.0;
  g_oup : vgs == igs * 1.0;
  
--  flag == 1.0;
 
---- Current is in Micro Amps.

  ------ Cut OffRegion
    if((vgs >= 0.0) and (vgs <= vth)) use
	gnc :    idsg == 0.0;

  ------ Linear Region
  elsif((vds <= (vgs-vth)) and (vds > 0.0)) use
      	gnl :    idsg == hfe*(((vgs-vth)*vds) - (pow(vds,2.0)/2.0));
 
  ------ Saturation Region
  elsif((vds > (vgs-vth)) and (vgs > vth)) use
      gns2 : idsg == (hfe/2.0)*(pow((vgs-vth),2.0));

  ------ Other conditions
 -- elsif(vgs < 0.0 or vds <= 0.0) use
  elsif(1.0 = 1.0) use
      temp : idsg == 0.0;
  end use;

end architecture behav; --- of nmos;

--------- Inverter Test Bench

-------*****************************************************************
--                   New Entity Begins : CMOS INVERTER
-------*****************************************************************

use work.electricalsystem.all;

entity inverter is
  port(inv_inp : in bit;
       inv_op : out bit);
end entity inverter;

architecture behav of inverter is

  terminal iin, iout, idd : electrical;
  quantity vdd across idd to electrical'reference;
  quantity vin across iin to electrical'reference;
  quantity vout across irout through iout to electrical'reference;
  
  constant power : real := 5.0;

  component nmos is
    port (terminal g,s,d : electrical);
  end component;
  for all : nmos use entity work.nmos(behav);

  component pmos is
    port (terminal g,s,d : electrical);
  end component;
  for all : pmos use entity work.pmos(behav);

  component a2d_comp is
     generic(vlo : real := 0.0;
             vhi : real := 10.0;
	     ped : time := 1 ns);
     port (signal input : in bit;
	   terminal pos, neg : electrical); 
  end component;
  for all : a2d_comp use entity work.a2d1bit(behav);

  component resistor_comp 
    generic ( r : real := 1.0);
    port ( terminal tr1, tr2 : electrical );
  end component;
  for all : resistor_comp use entity work.resistor(rbehavior);

begin
  
  vdd == power;

  sqr : a2d_comp  
	generic map(0.0, 10.0,  500 ps)
	port map(inv_inp, iin, electrical'reference);

  nm : nmos port map(iin, electrical'reference, iout);
  pm : pmos port map(iin, idd, iout);

  res_out : resistor_comp 
    generic map(5000000.0)
    port map(iout,electrical'reference);

  a2d: process 
  begin
    if(vout'above(0.003) = true) then
      inv_op <= '1';
    else
      inv_op <= '0';
    end if;
  end process;

end architecture behav; ---- of inverter 

-------*****************************************************************
--                   New Entity Begins : TESTBENCH
-------*****************************************************************

use std.textio.all;

entity test_bench is
end test_bench;

architecture tb_arch of test_bench is

component inverter_comp
  port(inv_inp : in bit;
       inv_op : out bit);
end component;

for all : inverter_comp use entity work.inverter(behav);

signal ip, op : bit;

begin

  i1 : inverter_comp
    port map(ip, op);

  inputtestbench:PROCESS
  begin
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    ip <= '0';
    wait for 100 NS;
    ip <= '1';
    wait for 100 NS;
    
    END process;

  testbench:PROCESS
    VARIABLE outline : LINE;
    VARIABLE Headline   : string(1 TO 54) :=
      "time inv_input inv_output";
    VARIABLE   seperator    : string(1 TO 1) := " ";
    VARIABLE   flag     : bit := '0';
    FILE outfile: text OPEN WRITE_MODE IS "Output.out";
  BEGIN
    IF (flag = '0') THEN
      flag := '1';
      WRITE(outline,Headline);
      WRITELINE(outfile,outline);
    ELSE
      WRITE(outline, now);
      WRITE(outline,seperator);
      WRITE(outline,ip);
      WRITE(outline,seperator);
      WRITE(outline,op);
      WRITELINE(outfile,outline);
    END IF;
    WAIT ON ip, op;
  END PROCESS;

end;