tiny-xo2-uart-loader/top.vhd

-------------------------------------------------------------------------------
-- Title      : MachXO2 Serial Configuration
-- Project    : tiny-xo2
-------------------------------------------------------------------------------
-- File       : top.vhd
-- Author     : マリオ  <mario.huettel@gmx.net>
-- Company    : 
-- Created    : 2017-11-21
-- Last update: 2017-11-21
-- Platform   : 
-- Standard   : VHDL'93/02
-------------------------------------------------------------------------------
-- Description: 
-------------------------------------------------------------------------------
-- Copyright (c) 2017 GPLv2
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity config_top is

  generic (
    CLKDIV : integer := 10);

  port (
    clk     : in  std_logic;            -- input clock 12 MHz
    dts     : in  std_logic;            -- DTS Strobe signal
    rst_out : out std_logic;
    uart_tx : out std_logic;            -- UART TX
    uart_rx : in  std_logic);           -- UART RX

end entity config_top;


architecture RTL of config_top is
  ----------------- RESET LOGIC ------------------------------
  signal dts_sync      : std_logic_vector(2 downto 0) := (others => '0');
  signal rst           : std_logic;     -- reset (high active)
  ----------------- UART RX ----------------------------------
  signal data_rx       : std_logic_vector(7 downto 0);
  signal byte_ready_rx : std_logic;
  signal error_rx      : std_logic;
  ----------------- UART TX ----------------------------------
  signal data_tx       : std_logic_vector(7 downto 0);
  signal byte_ready_tx : std_logic;
  signal busy_tx       : std_logic;


  signal config_busy : std_logic := '1';  -- indicates that the core is in configuration/waiting mode
  -- and the user logic has to stay in reset

begin  -- architecture RTL


  uart_rx_1 : entity work.uart_rx
    port map (
      clk          => clk,
      rst          => rst,
      data         => data_rx,
      byte_ready   => byte_ready_rx,
      error        => error_rx,
      ckDiv        => CLKDIV,
      parityEnable => '1',
      parityOdd    => '0',
      twoStopBits  => '0',
      rx           => uart_rx);

  uart_tx_1 : entity work.uart_tx
    port map (
      clk          => clk,
      rst          => rst,
      data         => data_tx,
      byte_ready   => byte_ready_tx,
      busy         => busy_tx,
      ckDiv        => CLKDIV,
      parityEnable => '1',
      parityOdd    => '0',
      twoStopBits  => '0',
      tx           => uart_tx);


  timeout_counter_gen : process(clk) is
    variable cnt : integer range 0 to 40000;
  begin
  -- TODO: implement timeout counter
  end process timeout_counter_gen;


  -- Generate reset pulse on rising edge of dts input
  reset_gen : process(clk) is
  begin
    if rising_edge(clk) then
      rst      <= '0';
      dts_sync <= dts_sync(1 downto 0) & dts;  -- Shif register (sync and edge detect)
      if (dts_sync(2 downto 1) = "01") then    -- rising edge of DTS
        rst <= '1';
      end if;
    end if;
  end process reset_gen;


  -- hold user logic in reset until config finished or timeout
  user_logic_reset_gen : process(clk, rst) is
  begin
    if rst = '1' then
      rst_out <= '1';
    elsif rising_edge(clk) then
      if config_busy = '0' then
        rst_out <= '0';
      end if;
    end if;
  end process user_logic_reset_gen;


  ------ Asynchronous output assignments ---------------

end architecture RTL;