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發表於 2009-1-10 22:11:05
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4 M( l$ d% s- r& H5 o- X8 F - library IEEE;& E- T2 Z. ]. `$ I
- use IEEE.std_logic_1164.all;
" X" t$ Q- H) C7 _ Q# J7 \ - entity fifo is) w6 W- a7 A5 [* p0 K
- generic (
: h, t1 i# W Y& k- b. \. T - depth : positive := 16' U7 J3 w' I I; l
- );
. F' q1 N2 Q, H$ h* N - port(
3 u* X' U6 q: |" r+ z - CLR : in std_logic;1 {# t) b5 H4 G4 Z
- WCLK : in std_logic;9 ]3 t- u& t) C9 @5 `, r9 a* a# B
- WE : in std_logic;. ^' P a3 T' I4 U( T# F+ o0 {9 j
- RCLK : in std_logic;
1 m7 ?$ o ?* X, i A - RE : in std_logic;3 e3 ~" Y3 U% s4 R; [
- DATA : in std_logic_vector(7 downto 0);
7 o* x6 e: B) E2 b* W. C; z* v - EMPTY : out std_logic;
6 r9 [# s8 b+ W0 H3 D8 _ - FULL : out std_logic;/ X8 V6 m# Y2 q& G" M
- Q : out std_logic_vector(7 downto 0)
- H: d! Z$ A+ t1 m d - );
; L7 A7 V8 h- g A7 ?- h0 q - end entity;
C6 y7 ` d$ W5 y4 x( t - library IEEE;
8 E, o! L) i) _& W+ ~$ v5 } - use IEEE.std_logic_unsigned.all;
2 W) ]5 \# z5 K6 j( S; {' e0 | - architecture behavior of fifo is
* T" D0 g# p: `( Q1 t6 h2 p$ k& d - constant fmax : positive := depth-1; g1 ^. F: ]7 g4 J3 \: u; }
- type fifo_array_type is array (fmax downto 0) of std_logic_vector(7 downto 0);. _$ r9 u1 |6 o; }& w7 R3 I3 d
- signal fifo_array : fifo_array_type; J8 q" O* V: _" ?" L: v) D* F1 Z4 u
- signal WR_PTR : INTEGER range 0 to fmax;
4 |8 l7 P. T* n0 X6 N1 z - signal RD_PTR : INTEGER range 0 to fmax;! Y" `/ M9 A' C: u5 _; p, T1 [
- signal count : INTEGER range 0 to depth;
& p M) B# N: D+ z; V4 I& } - begin- O2 ^% p, y) k8 M; d
- CNT: process(CLR, WR_PTR, RD_PTR), ~ R: K" m' T
- variable change : integer; L# w" e; [0 G; A% G( v
- begin 4 P( D* r% s! `/ ?2 C0 f' a8 J' D
- if CLR = '1' then
8 p- b/ m+ u7 N - count <= 0;/ g B7 U- t1 v4 `
- change := 0;
4 L2 U( z4 s4 r, ` - else0 X1 `5 r8 K# g1 i! r4 `! m& z
- change := 0;2 F. q. b7 V, f& u' A8 x
- if WR_PTR'event then/ v( X- q8 x2 y$ _! l+ e
- change := 1; s) U- c5 i$ j- i7 [5 ~2 ]; G+ [
- end if;
/ r! D$ l& I- o. |, o6 g1 S- V - if RD_PTR'event then
5 Q. T- b9 s; W2 P& B- J t$ N y - change := change - 1;! `1 A4 u% _5 A5 j& M$ b/ s
- end if;
! E! R4 q: F0 P5 M# v - count <= count + change;
- Z! o' z. r V! j4 z1 z - end if;
L$ R R; v/ Q- V% ] - end process; : {4 t6 L4 e- n, k6 y4 u) P0 ?
- STATUS: process(count)' D6 ~+ k- B" d5 G$ ?" Y' }
- begin ; p- u `8 \* m$ U' ]& C" O% b
- if count=0 then
$ \4 \+ ]$ g0 o7 e8 D+ p5 p6 J P - FULL <= '0';
* Y$ T2 k' y7 e1 G. U0 G2 ] - EMPTY <= '1';
4 q4 ]: l" S1 t' s, s; E$ I - elsif count=depth then
m, z; {4 a+ n* U - FULL <= '1';
; h7 W% W) h' D8 l. Z' E$ L6 L - EMPTY <= '0'; 5 i; [8 F) A' Y; t+ x9 S$ H
- else $ o } \+ t+ P# ?$ T" V# a
- FULL <= '0';
- D: Q t5 ], F2 V. R" y) M - EMPTY <= '0';
2 p0 l* `6 |7 D1 [ u7 v7 g5 K - end if; ; B O- j3 A( Q+ i# C- g* M
- end process;
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