io/eth/rst.vhd (902aa40) - mips_sys · BlinkenArea

rst.vhd

-- MIPS I system
-- Copyright 2011-2012 Stefan Schuermans <stefan@blinkenarea.org>
-- Copyleft GNU public license V2 or later
--          http://www.gnu.org/copyleft/gpl.html

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.NUMERIC_STD.ALL;

ENTITY e_io_eth_rst IS
    PORT (
        rst:        IN  std_logic;
        clk:        IN  std_logic;
        pin_o_nrst: OUT std_logic
    );
END ENTITY e_io_eth_rst;

ARCHITECTURE a_io_eth_rst OF e_io_eth_rst IS

CONSTANT c_rst_dur: natural := 5000;

SIGNAL r_rst_cnt: natural RANGE 0 TO c_rst_dur - 1 := 0;

SIGNAL r_nrst: std_logic := '0';

BEGIN

p_rst: PROCESS(rst, clk)
    BEGIN
        IF rst = '1' THEN
            r_rst_cnt <= 0;
            r_nrst    <= '0';
        ELSIF rising_edge(clk) THEN
            IF r_rst_cnt = c_rst_dur - 1 THEN
                r_nrst <= '1';
            ELSE
                r_rst_cnt <= r_rst_cnt + 1;
            END IF;
        END IF;
    END PROCESS p_rst;

pin_o_nrst <= r_nrst;

END ARCHITECTURE a_io_eth_rst;

mips_sys

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