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發表於 2009-1-10 22:11:05
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4 R7 J! R4 H( E - library IEEE;
* ]- N$ @/ w) M {4 i2 ^ - use IEEE.std_logic_1164.all;
! b- i! [; _1 ]3 K - entity fifo is1 e, X3 T4 z$ ~
- generic (
) c% U2 R `) O; ~# S2 m& Z - depth : positive := 16
+ s0 i: I' q2 g; d' d - );
9 L6 f5 l) Y6 G8 l - port(
L6 J2 |7 A- |. J1 O' ` - CLR : in std_logic;7 V) g p" D7 k1 D+ k. Q' M) X
- WCLK : in std_logic;' S3 j9 r! k( R; z
- WE : in std_logic; y4 Y, k! ^/ n; E d0 O
- RCLK : in std_logic;& K! [/ z" ?8 }; O" r
- RE : in std_logic;1 {/ ` S' X I' h
- DATA : in std_logic_vector(7 downto 0);
& ^4 }9 n9 F3 ?; o( a - EMPTY : out std_logic;
" d1 {7 \& j% p! k+ A0 M- S& \ - FULL : out std_logic;
; a7 `# I: t l: v" [ - Q : out std_logic_vector(7 downto 0)
% ?# W+ k: D( H! z - );
, i4 p% V5 O3 M2 k - end entity;: D( ^+ j) Y N8 W7 P$ F: r
- library IEEE;3 H$ x7 r; X0 p0 m
- use IEEE.std_logic_unsigned.all;8 {, D% C$ n( N; p( z
- architecture behavior of fifo is" T, T8 n: y p4 y, d9 K) [9 _
- constant fmax : positive := depth-1;
5 |! `# L8 g: E4 m2 [+ | - type fifo_array_type is array (fmax downto 0) of std_logic_vector(7 downto 0);
2 T! _0 B- z% s& ~* Y - signal fifo_array : fifo_array_type;
) G7 R! i4 C3 L$ Z5 {% [' J: s - signal WR_PTR : INTEGER range 0 to fmax;/ t5 e* C R \" P4 L: a( @
- signal RD_PTR : INTEGER range 0 to fmax;
1 _* C( X/ I- n* s6 n - signal count : INTEGER range 0 to depth;
: `3 N B. Y2 g4 A; Z% ^8 M" [' f - begin1 a$ D, c3 e: F( G7 v
- CNT: process(CLR, WR_PTR, RD_PTR)
5 W) X5 t* }& A: w( ], a+ { - variable change : integer; @3 _, g& i: h8 x% @/ r$ `
- begin
7 }' Z m3 g# e4 c) D; w - if CLR = '1' then1 U9 s U# E: D' c
- count <= 0;! s+ g* J( |7 a8 u
- change := 0; K( H1 w- X/ @- ~: _
- else- D X$ O# R) W+ T( Q2 z- m7 F
- change := 0;5 `' G# J' W: h# z
- if WR_PTR'event then
! F) M4 u3 c n- S! F6 p - change := 1;! O! Q" S/ p3 q7 ~) t- v- i' j
- end if;# e D! Z/ Q. V0 Q2 o! A
- if RD_PTR'event then7 Z3 f# b) Q9 R9 ^4 c0 B
- change := change - 1;
o9 E" l2 F2 R. S1 B& B6 u$ I - end if;, [+ G! O3 Q" ~5 c O
- count <= count + change;
) {9 D4 L% R, p9 L - end if;
/ f- K2 P& s+ z+ Y' @, ^5 D - end process; $ g, H; C! v7 `
- STATUS: process(count)0 J( Z$ o* ^: V
- begin
& H$ C6 S. v$ b) m1 E" O9 c - if count=0 then
! W$ {6 C1 ~- @, F3 g - FULL <= '0';" d( P& Y! D: ?( I- o
- EMPTY <= '1';1 t1 z; N, K" S( l8 I+ D1 ? w
- elsif count=depth then
}' f/ ^+ q: Y, T. i; {; h - FULL <= '1'; 8 E: k5 Q7 w- e8 D9 M% I
- EMPTY <= '0';
( z8 m5 t; Q R7 m5 q* X& P - else
! W/ c# ~( S/ U% Q5 O1 j - FULL <= '0';
2 p: V0 m" s6 j& W5 u# e - EMPTY <= '0'; 8 l" z$ o0 }( R! O ~* U
- end if;
2 c3 h" }5 m3 r) D4 d3 d - end process;
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