readfifo_rs232.vhd

ISE7.1

--------------------------------------------------------------------------------
-- Company: 
-- Engineer:
--
-- Create Date:    22:58:20 01/21/07
-- Design Name:    
-- Module Name:    readfifo_RS232 - Behavioral
-- Project Name:   
-- Target Device:  
-- Tool versions:  
-- Description: 用来控制串口发送命令的。
--
-- Dependencies:
-- 
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
-- 
--------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

---- Uncomment the following library declaration if instantiating
---- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity readfifo_RS232 is
port(
     reset             :in std_logic;
     rs232_clk_read    :in  std_logic;  -----采样EMPTY的时钟	可以用bclk。
     txd_done          :in std_logic;
	  fifo_empty        :in std_logic;------根据FIFO的空标志，只要非空则可以读，即发送串口发送命令
	  fifo_enable       :out std_logic;
	  trans_com         :out std_logic-----串口发送命令
     ) ;
end readfifo_RS232;

architecture Behavioral of readfifo_RS232 is
type states is(idle,rd_en_trcom_generate,cmd_cancel);
signal state:states:=idle;

	begin
		process(reset,rs232_clk_read,fifo_empty)
		begin
			if reset='0'then 
			   state<=idle;
				fifo_enable<='0';
				trans_com<='0';
			elsif rising_edge(rs232_clk_read)then
			   case state is
				    when idle=>
					      fifo_enable<='0';
							trans_com<='0';
					      if fifo_empty='0' then
							   state<=rd_en_trcom_generate;
							else
								state<=idle;
							end if;
			       when rd_en_trcom_generate=>
					      fifo_enable<='1';
							trans_com<='1';
							state<=cmd_cancel;
					 when cmd_cancel=>
					      fifo_enable<='0';
							trans_com<='0';
							 if txd_done='1'then 
							    if fifo_empty='1'then
								 state<=idle;
								 else
								   state<=rd_en_trcom_generate;
			                end if;
			             else
							      state<=cmd_cancel;
			             end if;
					end case;
			end if;		      
		end process;

	end Behavioral;