-- Greg Stitt
-- University of Florida

-- The following entity is the top-level entity for lab 2. No changes are
-- required, but you need to map the I/O to the appropriate pins on the
-- board. 

-- I/O Explanation (assumes the switches are on side of the
--                  board that is closest to you)
-- switch(9) is the leftmost switch
-- button(1) is the top button
-- led5 is the leftmost 7-segment LED
-- ledx_dp is the decimal point on the 7-segment LED for LED x

library ieee;
use ieee.std_logic_1164.all;

entity top_level is
    port (
        switch  : in  std_logic_vector(9 downto 0);
        button  : in  std_logic_vector(1 downto 0);
        led0    : out std_logic_vector(6 downto 0);
        led0_dp : out std_logic;
        led1    : out std_logic_vector(6 downto 0);
        led1_dp : out std_logic;
        led2    : out std_logic_vector(6 downto 0);
        led2_dp : out std_logic;
        led3    : out std_logic_vector(6 downto 0);
        led3_dp : out std_logic;
        led4    : out std_logic_vector(6 downto 0);
        led4_dp : out std_logic;
        led5    : out std_logic_vector(6 downto 0);
        led5_dp : out std_logic
        );
end top_level;

architecture STR of top_level is

    component decoder7seg
        port (
            input  : in  std_logic_vector(3 downto 0);
            output : out std_logic_vector(6 downto 0));
    end component;

    component alu_ns
        generic (
            WIDTH : positive := 16
            );
        port (
            input1   : in  std_logic_vector(WIDTH-1 downto 0);
            input2   : in  std_logic_vector(WIDTH-1 downto 0);
            sel      : in  std_logic_vector(3 downto 0);
            output   : out std_logic_vector(WIDTH-1 downto 0);
            overflow : out std_logic
            );
    end component;

    signal alu_out      : std_logic_vector(3 downto 0);
    signal alu_overflow : std_logic;
    signal alu_sel      : std_logic_vector(3 downto 0);

    constant C0 : std_logic_vector(3 downto 0) := "0000";

begin  -- STR

    -- map ALU output to rightmost 7-segment LED
    U_LED0 : decoder7seg port map (
        input  => alu_out,
        output => led0);

    -- all other LEDs should display 0
    U_LED1 : decoder7seg port map (
        input  => C0,
        output => led1);

    U_LED2 : decoder7seg port map (
        input  => C0,
        output => led2);

    U_LED3 : decoder7seg port map (
        input  => C0,
        output => led3);
    
    U_LED4 : decoder7seg port map (
        input  => C0,
        output => led4);

    U_LED5 : decoder7seg port map (
        input  => C0,
        output => led5);

    -- map the ALU select to the last 2 switches and the 2 buttons
    alu_sel <= switch(1 downto 0) & button;

    -- instantiate the ALU
    U_ALU : alu_ns
        generic map (
            WIDTH => 4)
        port map (
            input1   => switch(9 downto 6),  -- map input1 to the leftmost 4 switches
            input2   => switch(5 downto 2),  -- map input2 to the next 4 switches
            sel      => alu_sel,
            output   => alu_out,
            overflow => alu_overflow);

    -- map the alu overflow to the led0 decimal point, all others are off.
    led0_dp <= not alu_overflow;
    led1_dp <= '1';
    led2_dp <= '1';
    led3_dp <= '1';
    led4_dp <= '1';
    led5_dp <= '1';

end STR;