-- A sequential implementation of the vote-3 circuit using a
-- program-like procedural description.
--   (c) J. Dean Brock, 2004

library ieee ;
use ieee.std_logic_1164.all ;

entity VOTE3SPA is
  port (
        Reset:  in  STD_LOGIC;
        Clock:  in  STD_LOGIC;
        SerIn:  in  STD_LOGIC;
        SerOut: out STD_LOGIC
  );
end VOTE3SPA ;

architecture VOTE3SPA_arch_JDB of VOTE3SPA is
  type threecount is range 0 to 2 ;
begin  -- VOTE3SPA_arch_JDB

  process(Clock, Reset)
    VARIABLE CycleCount : threecount := 0 ;
    VARIABLE OneCount   : threecount := 0 ;
  begin
    if Reset = '1' then
      CycleCount := 0 ;
      OneCount := 0 ;
      SerOut <= '0' ;
    elsif Clock'event and Clock = '1' then
      if CycleCount = 2 then
        if OneCount = 2 or (OneCount = 1 and SerIn = '1') then
          SerOut <= '1' ;
        else
          SerOut <= '0' ;
        end if ;
        CycleCount := 0 ;
        OneCount := 0 ;
      else
        SerOut <= '0' ;
        CycleCount := CycleCount + 1 ;
        if SerIn = '1' then
          OneCount := OneCount + 1 ;
        end if ;
      end if ;
    end if ;
  end process ;
  
end VOTE3SPA_arch_JDB;