fifo.vhd

fifo的vhdl代码,比较简单

library IEEE;
use IEEE.Std_logic_1164.all;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

entity CFIFO is
   generic(m, n : Positive := 4); --m is depth, n is width
   port(RST,CLK,WRREQ, RDREQ : in Std_logic;
         DATAIN : in Std_logic_vector((n-1) downto 0);
         DATAOUT : out Std_logic_vector((n-1) downto 0);
         FULL, EMPTY : out Std_logic);
end CFIFO;

architecture V2 of CFIFO is
   type FIFOM is array(0 to (m-1)) of Std_logic_vector((n-1) downto 0);
   signal CFIFO_memory : FIFOM;
   signal Wraddr, Rdaddr, Offset : Natural range 0 to (m-1);
   signal Rdpulse, Wrpulse, Q1, Q2, Q3, Q4,FI,EI : Std_logic;
   signal Databuffer : Std_logic_vector((n-1) downto 0);
begin
	CFIFO_write : process
	begin
		  wait until rising_edge(CLK);
		  if RST = '1' then  Wraddr <= 0;
		  elsif (Wrpulse = '1' and FI = '0') then
			 CFIFO_memory(Wraddr) <= DATAIN;
			 Wraddr <= (Wraddr + 1) mod m;----Natural
		  end if;
	end process;
	
	CFIFO_read : process
	begin
		  wait until rising_edge(CLK);
		  if RST='1' then Rdaddr <= 0;  Databuffer<= (others => '0');
		  elsif (Rdpulse = '1' and EI = '0') then
			 Databuffer<=CFIFO_memory(Rdaddr);  Rdaddr<=(Rdaddr+1) mod m;
		  end if;
	end process;
		   
	sync_ffs : process
    begin
			wait until rising_edge(CLK);
			Q1 <= WRREQ;		Q2 <= Q1;---1
			Q3 <= RDREQ;		Q4 <= Q3;--1
	end process;
	
Wrpulse <= Q2 and not(Q1);	Rdpulse <= Q4 and not(Q3);   
Offset <= (Wraddr - Rdaddr) when (Wraddr > Rdaddr) 
            else (m - (Rdaddr - Wraddr)) when (Rdaddr > Wraddr)
            else 0;

 EI<= '1' when (Offset = 0) else '0';
 FI<= '1' when (Offset = (m-1)) else '0';

EMPTY<=EI;
FULL<=FI;
DATAOUT <= Databuffer when RDREQ = '0' 
            else (others => 'Z');
end V2;