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發表於 2009-1-10 22:11:05
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- ------------------------------------------------------------------------------------4 S/ v: Q7 h; H7 c; q
- library IEEE;
$ r' z$ s3 `! `! ` - use IEEE.std_logic_1164.all;/ K7 ]! N s3 h8 u6 g" N
- entity fifo is
: @3 J/ W& |2 {# } - generic (# W# w5 {4 j' Y4 m' K: Z3 K6 g( f
- depth : positive := 16
: x+ D; J5 P& U2 J0 `& O! y' h - );
' q5 ]9 ?4 z5 K - port(& s' q3 P# [6 ?! z
- CLR : in std_logic;5 _2 R" Z1 P" V, l
- WCLK : in std_logic;
# D3 M+ j/ _9 M4 r m8 e+ @ - WE : in std_logic;+ x* t0 C$ J! M6 s2 a \9 s
- RCLK : in std_logic;
1 G7 A4 w4 _' @. y7 B( p - RE : in std_logic;
" E; S2 D( b6 b- v# D - DATA : in std_logic_vector(7 downto 0);5 w) I# U r2 V$ N
- EMPTY : out std_logic;
1 n1 c0 G1 @9 _; _* f - FULL : out std_logic;
0 K- a+ x3 ~* I' i: I - Q : out std_logic_vector(7 downto 0)+ V/ o x1 a0 V! _- e( W& ~6 G* H/ v
- );5 c+ G5 T4 E/ i$ n
- end entity;0 u+ ~. y5 k2 {
- library IEEE;8 D/ r9 O7 U/ ?, y2 q7 K
- use IEEE.std_logic_unsigned.all;/ ]1 o* m" f1 @7 M9 G4 C
- architecture behavior of fifo is% T. C- f# k8 z, o! E6 E
- constant fmax : positive := depth-1; - \% G- C8 F/ \& }3 |: q
- type fifo_array_type is array (fmax downto 0) of std_logic_vector(7 downto 0);
6 P7 y0 X5 C6 B0 ^8 h& i- @ - signal fifo_array : fifo_array_type;
- \" p: x2 i* z; @ - signal WR_PTR : INTEGER range 0 to fmax;) J3 ]( I& q6 u* n; f' I$ K
- signal RD_PTR : INTEGER range 0 to fmax;
[3 ]% R { J5 p* t4 ] - signal count : INTEGER range 0 to depth;$ I" N6 G, M2 j9 M0 |
- begin0 P5 a9 w3 R, D% H
- CNT: process(CLR, WR_PTR, RD_PTR)) m p* d/ g3 i) f" i
- variable change : integer;
. `% u A; i8 v x& w- ]/ z# } - begin
- f" v$ @/ r1 f3 R5 N - if CLR = '1' then
# H. s" p* M# V. Q, k2 w - count <= 0;4 |; [* r7 p d& ^; q$ O7 @1 K, a
- change := 0;
h1 D0 d/ w! q1 ~ - else9 d' O- a9 z! C0 h9 Q( ~% a
- change := 0;: o9 e+ q/ r& g3 H0 @( Z
- if WR_PTR'event then
! o3 H% x+ b8 H `& F5 i) \ - change := 1;
`8 j6 o* B# {8 h" N* V; c - end if;
) D2 ]8 S+ o/ n - if RD_PTR'event then
1 N. P7 ?1 c" e4 B - change := change - 1;5 C3 ? Z5 H: @9 P
- end if;
, Q6 V4 S: X; t - count <= count + change;3 u- Z( q, Z4 \6 ^' ^( Q
- end if;
% y7 i& p# _' ]4 D% \7 }. ? - end process;
1 n* c9 d: X0 I7 r J. i - STATUS: process(count)
" t, u7 G' }& G. h - begin : y( V/ m' X# b s" Q$ |2 O
- if count=0 then' c' a6 T) j/ R6 v
- FULL <= '0';* L' N! b4 T/ y4 ]1 |
- EMPTY <= '1';
4 I# f* c6 a, o: o1 j; y; G4 h - elsif count=depth then ^5 p7 L' V( _, u, c! d* a$ T
- FULL <= '1'; 4 U8 D9 j" T) r) q6 t
- EMPTY <= '0'; 1 w* v2 ^7 {: J( x
- else }9 l- O% Z! @2 x0 H
- FULL <= '0'; . s- A- ?; B/ ]6 A+ R2 W
- EMPTY <= '0';
8 e& g( g) i) ]3 v e( C( m! k - end if; ' V: T, H# R: L
- end process;
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