s2f.vhd

以太网到电信网转换的网关（简易版）

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--
-- Title       : S2F
-- Design      : gateway
-- Author      : zlm
-- Company     : buaa
--
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--
-- File        : S2F.vhd
-- Generated   : Wed Dec 15 19:44:43 2004
-- From        : interface description file
-- By          : Itf2Vhdl ver. 1.20
--
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--
-- Description : 
--
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--{{ Section below this comment is automatically maintained
--   and may be overwritten
--{entity {S2F} architecture {S2F}}

library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;


entity S2F is
	 port(
		 reset : in STD_LOGIC;
		 clk : in STD_LOGIC;
		 din1 : in STD_LOGIC;
		 din2 : in STD_LOGIC;
		 din3 : in STD_LOGIC;
		 din4 : in STD_LOGIC;
		 is_empty : in STD_LOGIC_VECTOR(3 downto 0);
		 enable : out STD_LOGIC;
		 rd : out STD_LOGIC_VECTOR(3 downto 0);
		 dout : out STD_LOGIC_VECTOR(3 downto 0)
	     );
end S2F;

--}} End of automatically maintained section

architecture S2F of S2F is

constant idlecode:std_logic_vector(3 downto 0):="0000";
signal reg:std_logic_vector(3 downto 0);
signal flag:std_logic; 
signal flag2:std_logic;

begin
 
process(clk,reset)

begin
	if reset='1'then
		enable<='0';
		rd<="1111";
		dout<=(others=>'0');
		reg<=idlecode;
		flag<='0';
		flag2<='0';
	elsif clk'event and clk='1'then
		if is_empty="0000" then
			rd<="0000";
			flag<='1';
		else
			rd<="1111";
			flag<='0';
		end if;
		
		if flag='1'then
			flag2<='1';
			dout<=reg;
			reg(3)<=din1;
			reg(2)<=din2;
			reg(1)<=din3;
			reg(0)<=din4;
		else
			flag2<='0';
			dout<=reg;
			reg<=idlecode;
		end if;	
		
		if flag2='1'then
			enable<='1';
		else 
			enable<='0';
		end if;
		
		
	end if;
end process;
end S2F;