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發表於 2009-1-10 22:11:05
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- ------------------------------------------------------------------------------------
# T t. ]6 B8 G7 D$ C' b8 {! u9 F - library IEEE;
* h- Y/ \; g8 T4 Y. a - use IEEE.std_logic_1164.all;5 d9 U5 m+ U' W- A) y
- entity fifo is
; Q' _% v2 R) r3 r: l' Y - generic (
+ j( r2 q, L' P C* X - depth : positive := 16
p( \7 u- _5 q/ p5 `" Y: Q - );
1 \* f2 a8 I9 _6 l6 \ - port(+ S' j, h. u+ e2 ]' C% _
- CLR : in std_logic;
8 x2 u2 A4 b4 i8 r- M/ D - WCLK : in std_logic;
0 U" N8 F4 P5 f w: p - WE : in std_logic;* A! j( m! B9 t- B/ A0 m" N3 D4 X; p! l
- RCLK : in std_logic;
: J) |! X |( D ?9 { I - RE : in std_logic;' } a4 u P4 F9 e2 E# ^( D
- DATA : in std_logic_vector(7 downto 0); V/ K ?5 R }( B! o% F
- EMPTY : out std_logic;9 j* W, V+ v o; }; T2 a
- FULL : out std_logic;
2 l9 m, `: l$ q1 i4 j5 C1 u - Q : out std_logic_vector(7 downto 0)- I# T# O) m4 S. I, g) x" B
- );
1 S3 ^0 ^; v- ? - end entity;! g6 ? H+ [2 j8 U* @
- library IEEE;
( Z* T7 n l6 m8 f+ d: O - use IEEE.std_logic_unsigned.all;
; j# W e& Y: w - architecture behavior of fifo is* z v$ y( B+ [& f3 A P/ i: `
- constant fmax : positive := depth-1; 7 q! c+ j! K) l# D
- type fifo_array_type is array (fmax downto 0) of std_logic_vector(7 downto 0);, T5 [3 o$ _8 }/ M, @. N
- signal fifo_array : fifo_array_type;4 u* y7 j7 |3 T3 T8 ~+ t
- signal WR_PTR : INTEGER range 0 to fmax;
+ M& }3 M( Q2 B* r - signal RD_PTR : INTEGER range 0 to fmax;% w; L& _/ y3 |
- signal count : INTEGER range 0 to depth;! h% g0 A; E8 \$ o0 X
- begin7 Q9 W% ~& G+ }( I
- CNT: process(CLR, WR_PTR, RD_PTR); m5 J& a# b, u8 \+ T$ u
- variable change : integer; 4 {0 O" P, y+ L h% x
- begin
/ F' F( h7 P; K. A - if CLR = '1' then/ q9 e8 _! \; O3 v4 V
- count <= 0;
! }9 Q7 v- w0 F( r/ ]: k& | - change := 0;
& K2 q* S) Q% z" K - else
) h$ |) O0 |+ H - change := 0;( H( i- I6 S5 z+ P2 Q
- if WR_PTR'event then
?* _; |% y9 ^& x0 [ - change := 1;
7 b' J/ H& w4 F- e+ R - end if;6 H" F' V$ }* n+ A( b' [
- if RD_PTR'event then3 @# f3 _& c8 s6 g$ j' @
- change := change - 1;. _/ a! C4 X6 R& `* \9 A& y7 y; Q
- end if;9 C' f# N! w k" [
- count <= count + change;
8 B/ x: {' i( w. m: ^* W' _ r2 y: t - end if;
) d: ]- B* {8 G) ^" L - end process;
( Y% w' r- A* x7 t4 n/ K - STATUS: process(count)! L i5 Q2 u. h" w( G
- begin
" W& c8 F3 C; E" T/ L3 t8 z& Z _5 Y8 H - if count=0 then6 u4 C( R1 U" W) S8 p
- FULL <= '0';
/ E0 y! \; I( D6 [1 ]6 S4 p - EMPTY <= '1'; r8 d$ {3 q6 d- y
- elsif count=depth then# s2 T) p; C8 `3 `9 u. Z2 w* E
- FULL <= '1';
0 ]6 x& D: h3 u - EMPTY <= '0';
: i, i# _# W; K' R5 n - else $ E/ N; u3 s \, c9 f. d
- FULL <= '0';
v$ ^! ]+ K$ } - EMPTY <= '0';
6 T3 W( U. d9 G8 Q. h+ D1 G - end if;
" @, B ^( |5 P$ T9 U - end process;
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