-------------------------------------------------------------------------------
-- 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 
-- are copyrighted works of Mentor Graphics. USE OF THIS MODEL INDICATES YOUR 
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-- notice that this model has been modified and the date of modification; and 
-- (d) any compilations sold by you that include this model must include a 
-- conspicuous notice that this model is available from Mentor Graphics in its
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--
-- THIS MODEL IS LICENSED TO YOU "AS IS" AND WITH NO WARRANTIES, EXPRESS OR 
-- IMPLIED.  MENTOR GRAPHICS SPECIFICALLY DISCLAIMS ALL IMPLIED WARRANTIES OF 
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-------------------------------------------------------------------------------
-- File       : sw_1p3t.vhd
-- Author     : Mentor Graphics
-- Created    : 2003-04-18
-- Last update: 2003-05-13
-------------------------------------------------------------------------------
-- Description: Single-pole triple-throw electrical switch
-------------------------------------------------------------------------------
-- Revisions  :
-- Date        Version     Author              Description
-- 2003-04-18  1.0         Mentor Graphics     Created    
-------------------------------------------------------------------------------
-- Notes:
-- 1. Integer value on ctrl port determines switch position.
-- 2. Use sw_ctrl.vhd model in SystemVision model library
-------------------------------------------------------------------------------

library IEEE;
use IEEE.std_logic_1164.all;
-- Use IEEE natures and packages
use IEEE.electrical_systems.all;

entity sw_1p3t is
  generic (r_open   : resistance := 1.0e6;    -- Open (off) resistances
           r_closed : resistance := 1.0e-3;   -- Closed (on) resistances
           td_make  : real       := 1.0e-9;   -- time to "make" contacts
           td_break : real       := 1.1e-9);  -- time to "break" contacts  

  port (signal ctrl              : in integer;
        terminal com, p1, p2, p3 :    electrical);

end entity sw_1p3t;


architecture ideal of sw_1p3t is

  signal   r_sig1 : resistance := r_closed;  -- sets default to position 1
  signal   r_sig2 : resistance := r_open;
  signal   r_sig3 : resistance := r_open;
  quantity v1 across i1 through com to p1;     -- branch quantities 
  quantity v2 across i2 through com to p2;
  quantity v3 across i3 through com to p3;
  quantity r1     : resistance;              -- free quantities 
  quantity r2     : resistance;
  quantity r3     : resistance;

begin

  -- purpose: Detect Switch position and assign resistance value to r_sig
  -- type   : combinational
  -- inputs : ctrl
  -- outputs: r_sig
  DetectPosition : process (ctrl)
  begin
    -- position 1 (default) connects com to p1
    if (ctrl = 1) then
      r_sig1 <= r_closed;               -- signal assignments
      r_sig2 <= r_open;
      r_sig3 <= r_open;
      -- position 2 connects com to p2
    elsif (ctrl = 2) then
      r_sig1 <= r_open;
      r_sig2 <= r_closed;
      r_sig3 <= r_open;
      -- position 2 connects com to p3
    elsif (ctrl = 3) then
      r_sig1 <= r_open;
      r_sig2 <= r_open;
      r_sig3 <= r_closed;
    else
      -- undefined positions set all resistances to r_open
      r_sig1 <= r_open;
      r_sig2 <= r_open;
      r_sig3 <= r_open;
    end if;
  end process DetectPosition;

  r1 == r_sig1'RAMP(td_break, td_make);  -- use 'ramp attribute for linear
  r2 == r_sig2'RAMP(td_break, td_make);  -- transition between values
  r3 == r_sig3'RAMP(td_break, td_make);
  v1 == r1*i1;
  v2 == r2*i2;
  v3 == r3*i3;

end architecture ideal;

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