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發表於 2009-1-10 22:11:05
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% j8 |7 A; K) ^3 U& E$ z' ` - library IEEE;: v% }( Y5 m0 s$ E) e/ J( Z1 I
- use IEEE.std_logic_1164.all;
- L$ ]- n9 O$ K* S, }5 W0 f' w - entity fifo is
* [$ X0 K9 d' g - generic (
3 Z4 K! |- p' z$ D5 `' O - depth : positive := 16
+ `4 x; i, E {# @9 Z8 n - );
/ X a; @4 o. [2 V1 V - port(
) t1 M+ p/ E" \ [( y, a - CLR : in std_logic; I- @3 D( r' \1 g
- WCLK : in std_logic;
4 l$ J3 B7 j) X& g - WE : in std_logic;0 X/ ~& r0 \0 F! j! d- q6 ]1 i% I
- RCLK : in std_logic;; R. r# R% |& r# G% \
- RE : in std_logic;( _* ?0 g1 k2 ]: K% q4 \4 \
- DATA : in std_logic_vector(7 downto 0);
0 M7 p9 s' I' R3 X) f0 h - EMPTY : out std_logic;1 _3 R2 r! O) B5 ?
- FULL : out std_logic;
! [/ j1 d. u! `2 r - Q : out std_logic_vector(7 downto 0)+ W3 b2 G c) j S% ~
- );
! ^( V% N% J% n2 g) s0 V4 _7 ] - end entity;# s2 P6 A* _& {" m u9 M) D
- library IEEE;3 b4 N3 z& n6 z9 h* G9 L% W
- use IEEE.std_logic_unsigned.all;, A. r% n( ^- I6 T$ ?
- architecture behavior of fifo is' I" ]( l5 b. m% z! @/ |
- constant fmax : positive := depth-1;
9 T3 P: @8 z& m1 d1 a& d - type fifo_array_type is array (fmax downto 0) of std_logic_vector(7 downto 0);
/ G: Z+ G: Z' F: W2 g) ^ - signal fifo_array : fifo_array_type;
! L+ l/ t0 \% C/ {5 f! k* k @ - signal WR_PTR : INTEGER range 0 to fmax;
" K- S4 q- w# X4 {0 Q - signal RD_PTR : INTEGER range 0 to fmax;# n# W* k/ E$ t% B0 c2 l
- signal count : INTEGER range 0 to depth;. i4 n# i- N! |& j" ?) y K
- begin
" E" j1 T2 F& P2 D6 y2 g - CNT: process(CLR, WR_PTR, RD_PTR)
8 U) f2 g6 d O: L7 E - variable change : integer;
" s* a( G! i2 t; p8 P1 d - begin
! w: H' P1 j4 T* e. q8 s - if CLR = '1' then& S; N. Z3 ^5 [! b& O
- count <= 0;6 u7 z4 [3 L7 J9 ~% N
- change := 0;3 O/ C" O B9 ~. ~; v, q7 ]
- else
; D z, C- `2 Q2 }5 y - change := 0;8 r$ V7 X" E5 l4 r6 l
- if WR_PTR'event then
0 T, y- J7 S, f- y1 L9 a* a - change := 1;4 K" H# t2 g2 I' S, |* v
- end if;
) \& ~- M% U0 a5 t$ H - if RD_PTR'event then
p/ R% s5 ?& \7 I% _ - change := change - 1;" X" z6 N2 j. j6 p% c
- end if; C/ X! Z% @3 h f* O1 |
- count <= count + change;" i0 `9 B. I6 E- C+ N8 Z' o
- end if;
4 I4 q1 b5 i# A3 o - end process;
) V1 F: ~& j8 p. Q - STATUS: process(count)
) p' c% m, \& U0 Y& y$ G* R - begin : O$ H. d" c7 f, K' F$ E% B5 ?
- if count=0 then
6 ?: ]9 a* E$ R) p+ R - FULL <= '0';0 s% [$ @+ l% e1 T
- EMPTY <= '1';
9 m" E! s. q5 ^ - elsif count=depth then
, h0 j1 _6 d. F" t - FULL <= '1'; . c/ R( W2 u" Q4 e/ x& X
- EMPTY <= '0'; 5 X- g) S) A8 x+ t' G1 S$ ]3 D
- else 9 U( k# E# g8 V! J# U' k* `
- FULL <= '0';
; f& T2 ~8 t3 o5 W# P. @4 l - EMPTY <= '0'; 6 _! n5 B; ?% ~3 D# c
- end if;
' a7 ~, U+ i# ?( C* r - end process;
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