コンピューターアーキテクチャー / memoryを作りかえる

Chapter 5

テキストは下のようにメモリーマップしている。

• 0～16383番地: RAM
• 16384～24575番地: Screen
• 24576番地: Keyboard

ここではひとまず下のように割り当てておく。

• 0～63番地: RAM + Screen
• 64番地: Keyboard
  

library ieee;
use ieee.std_logic_1164.all;

entity memory is
    port (
        inp: in std_logic_vector(15 downto 0);
        clk: in std_logic;
        address: in std_logic_vector(14 downto 0);
        load: in std_logic;
        dip_sw: in std_logic_vector(15 downto 0);
        outp: out std_logic_vector(15 downto 0)
    );
end entity;

architecture behavior of memory is
    signal outp_ram64, outp_keyboard: std_logic_vector(15 downto 0);
begin
    ram: entity work.ram64
    port map (
        inp => inp,
        clk => clk,
        load => load,
        address => address(5 downto 0),
        outp => outp_ram64
    );
    
    keyboard: entity work.register_16_bit
    port map (
        clk => clk,
        load => '1',
        d => dip_sw,
        q => outp_keyboard
    );
    
    mux: entity work.mux16
    port map (
        a => outp_ram64,
        b => outp_keyboard,
        sel => address(6),
        outp => outp
    );
    
end architecture;