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發表於 2009-1-10 22:11:05
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8 w O: m3 N0 p: F- g- y - library IEEE;. h3 `0 Y1 i, U1 C# D
- use IEEE.std_logic_1164.all;) O9 z+ j9 m& `1 R
- entity fifo is7 n$ P- l* U6 b3 B q# C1 S. R% `3 K( R, o
- generic (
. _4 a7 ~2 k1 y* R" d6 @: y - depth : positive := 164 M! S8 ]4 f# O$ U5 {
- );
7 h5 [5 y/ X8 R$ } - port(
+ b8 N( \ ]7 L - CLR : in std_logic;
0 R& r# Z ]# z: u - WCLK : in std_logic;
7 d1 i7 x- n& o0 r. z P4 A5 |$ G - WE : in std_logic;9 v* j& n P! y, @0 X" U2 O
- RCLK : in std_logic;
; a4 X% F: _: e0 J9 H - RE : in std_logic;
5 e6 H/ C1 Y& R$ M - DATA : in std_logic_vector(7 downto 0);
F3 r+ O( D- O( f# o: R4 F$ C+ V& t - EMPTY : out std_logic;/ P6 ]; F# C& I4 s, R
- FULL : out std_logic;# U( s+ I% _+ ^9 P" Y i7 @
- Q : out std_logic_vector(7 downto 0)' \! W7 a4 k; X6 q! v \; F- ]
- );
/ H5 K% L" B, j& x+ |1 q - end entity;2 ~4 z* S) v( X D \+ @3 z
- library IEEE;
" l& A X6 u7 Z+ f+ g0 |& k0 [" q1 v - use IEEE.std_logic_unsigned.all;
1 m7 y$ ]/ |% Y- [" k1 G4 A+ W - architecture behavior of fifo is
0 s& |* _8 ?1 @% B - constant fmax : positive := depth-1;
/ }1 b% ]! Q7 W - type fifo_array_type is array (fmax downto 0) of std_logic_vector(7 downto 0);
v6 K. F3 W: j3 @ H* a I7 ? - signal fifo_array : fifo_array_type;
2 O4 x4 P, S& S- W; K% C/ ^. ?: { - signal WR_PTR : INTEGER range 0 to fmax;' C) k/ D, P5 p$ l1 `) R
- signal RD_PTR : INTEGER range 0 to fmax;9 A3 \. Y3 F- H9 b8 O
- signal count : INTEGER range 0 to depth;& M$ M9 S+ M, D2 \2 O
- begin) b' P" @+ C& Y. ]6 P
- CNT: process(CLR, WR_PTR, RD_PTR)
' m' P9 e7 w& H) e; R7 r - variable change : integer;
|: t( j6 E# Q# l% Q4 c$ i - begin
9 a9 G$ }* f- ^# c6 m3 Q- M% n - if CLR = '1' then
6 p5 o; v, c& p7 s/ A - count <= 0;
2 A8 v0 X6 A; r! W# R8 j9 y - change := 0;
: b% `4 x1 X7 T) ^. p6 G0 G# K3 ` - else8 Y' y) L- V9 D" w
- change := 0;
6 n% f: l$ u7 i m4 P - if WR_PTR'event then9 Y# G$ B% E. s* `
- change := 1;2 v& G a0 b: |. ~* y. u
- end if;9 H0 _$ u4 w, {5 V
- if RD_PTR'event then' t7 @3 ^( w! ~+ G" A3 P0 L: _
- change := change - 1;6 O5 [, V+ p; H% e
- end if;6 Q. H7 W& g& ]1 W; W% R& M9 f J
- count <= count + change;3 g: ^9 p1 R) C: l! N- u$ R
- end if;# s0 w! g9 `/ |9 P% J2 E
- end process; ! J) i! s0 z% ~* X- J
- STATUS: process(count)
3 `; s1 v5 N( v) b) U - begin
6 P$ Q9 Q& E( d - if count=0 then
4 w" a/ }* b" v+ Z" x( C2 j* B/ t, n - FULL <= '0';% L( D! l1 D% j% M4 V9 `- w
- EMPTY <= '1';/ k* k( j1 @* J1 x$ A" N: \
- elsif count=depth then4 Z) q1 U% h: I% _3 \2 {
- FULL <= '1';
# M2 w X! r, }- [' M6 G/ |2 O; y - EMPTY <= '0'; & ~# i. ~* _8 P$ t' M
- else
) `" _ N% I! I% N - FULL <= '0'; - o1 f% c; {0 D! U+ T
- EMPTY <= '0'; * C3 Q6 U2 h7 ^4 ?- R7 E, B
- end if;
j8 @& m5 f/ ~0 R2 n - end process;
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