ascount.vhd

4位MCU AM2901的完整VHDL程序

-- Synchronous Counter of Generic Size
--
-- Countersize--size of counter
--
-- clk--posedge clock input
-- areset--asynchronous reset
-- sreset--active high input resets counter to 0
-- enable--active high input enables counting
-- count--counter output
-------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_signed.all;

entity ascount is 
generic(countersize:integer:=2);
port(clk,areset,sreset,enable:in std_logic;
count:buffer std_logic_vector(countersize-1 downto 0));
end ascount;

architecture archascount of ascount is
begin
process(areset,clk)
begin
if areset='1' then
   count<=(others=>'0');
elsif rising_edge(clk) then
    if sreset='1' then
       count<=(others=>'0');
    elsif enable='1' then
          count<=count+1;
    else
          count<=count;
    end if;
end if;
end process;
end archascount;