Subversion Repositories am9080_cpu_based_on_microcoded_am29xx_bit-slices

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-- Company: 
-- Engineer: 
-- 
-- Create Date: 09/20/2017 10:32:16 PM
-- Design Name: 
-- Module Name: Am2922 - Behavioral
-- Project Name: 
-- Target Devices: 
-- Tool Versions: 
-- Description: 
-- 
-- Dependencies: 
-- 
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
-- 
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
 
-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;
 
-- Uncomment the following library declaration if instantiating
-- any Xilinx leaf cells in this code.
--library UNISIM;
--use UNISIM.VComponents.all;
 
entity Am2922 is
    Port ( clk : in STD_LOGIC;
           a : in STD_LOGIC;
           b : in STD_LOGIC;
           c : in STD_LOGIC;
           pol : in STD_LOGIC;
           nME : in STD_LOGIC;
           nRE : in STD_LOGIC;
           nCLR : in STD_LOGIC;
           nOE : in STD_LOGIC;
           d : in STD_LOGIC_VECTOR (7 downto 0);
           y : out STD_LOGIC);
end Am2922;
 
architecture Behavioral of Am2922 is
 
signal mux, muxen: std_logic;
signal q: std_logic_vector(3 downto 0) := "0000";
 
begin
 
muxen <= not nME;
mux <= not (
        (muxen and q(2)       and q(1)       and q(0)       and d(7)) or
        (muxen and q(2)       and q(1)       and (not q(0)) and d(6)) or
        (muxen and q(2)       and (not q(1)) and q(0)       and d(5)) or
        (muxen and q(2)       and (not q(1)) and (not q(0)) and d(4)) or
        (muxen and (not q(2)) and q(1)       and q(0)       and d(3)) or
        (muxen and (not q(2)) and q(1)       and (not q(0)) and d(2)) or
        (muxen and (not q(2)) and (not q(1)) and q(0)       and d(1)) or
        (muxen and (not q(2)) and (not q(1)) and (not q(0)) and d(0))
    );
y <= (q(3) xor mux) when (nOE = '0') else 'Z';
 
load_q: process(clk, a, b, c, pol, nCLR, nRE)
begin
    if (nCLR = '0') then
        q <= "0000";
    else
        if (rising_edge(clk) and (nRE = '0')) then
            q <= pol & c & b & a;
        end if;   
    end if;
end process;
 
end Behavioral;