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- ------------------------------------------------------------------------------------& Z ~" h" s R% ]$ h9 X
- library IEEE;. U& O3 i( \6 P) a6 S& g9 U3 V6 c9 T$ W
- use IEEE.std_logic_1164.all;0 C6 y1 r5 u& ^/ c* o8 s
- entity fifo is; Z' i$ Q7 m, |% R
- generic (
8 ~. t/ l9 g7 k0 d5 i( o$ O - depth : positive := 16
& N( Z, ~( D' B7 \* G. s0 w - ); ( M, k: E4 n' O; D1 j2 o
- port(
4 z: I) N1 ~4 W - CLR : in std_logic;% u$ B7 a4 ]$ Q" e& D" o+ e' B2 |
- WCLK : in std_logic;! c1 p9 A6 c5 e3 k2 K
- WE : in std_logic;/ {% v( v4 T a# r! W
- RCLK : in std_logic;+ h+ R1 Q0 d6 W4 i5 U9 d9 q5 n6 b
- RE : in std_logic;
' O. H" [* w& N/ s. w4 H; ~ - DATA : in std_logic_vector(7 downto 0);
5 [, Q& c8 u4 N. _ - EMPTY : out std_logic;! v/ m; k- g0 M2 [2 M
- FULL : out std_logic; U% {. x, C/ M- p& v
- Q : out std_logic_vector(7 downto 0)& I4 g. W( Q. ?" J B
- );# s( ~6 l6 p) l U4 D
- end entity;% }" D+ O+ n: x! a& V
- library IEEE;
2 K {9 f+ T5 o& X, B - use IEEE.std_logic_unsigned.all;
& A8 Y' q& ^( C2 n0 b5 k - architecture behavior of fifo is
) @9 V: @: q% _* e$ u6 R/ y9 S" y: Y - constant fmax : positive := depth-1;
- G, j( Q: q* z: B4 g2 s1 V - type fifo_array_type is array (fmax downto 0) of std_logic_vector(7 downto 0);/ |+ z% O$ f3 G+ i; S; y
- signal fifo_array : fifo_array_type;
9 v( p! {2 W( m6 Y9 l - signal WR_PTR : INTEGER range 0 to fmax;! e$ {$ D5 ^* i* @& G
- signal RD_PTR : INTEGER range 0 to fmax;6 F- t2 m) w3 @" H1 k0 a+ ]: ^
- signal count : INTEGER range 0 to depth;
3 z0 m! i6 ?' K- _) m - begin S2 \, _$ A: M W' {0 t4 |! ?) j
- CNT: process(CLR, WR_PTR, RD_PTR)
' d3 _9 @0 w) Y. j - variable change : integer;
5 L0 H7 g% v) I1 g - begin
' m0 [$ w$ l& C - if CLR = '1' then
9 j& S/ c8 j' F, }7 L# E - count <= 0;" G q5 b" ~& I, P1 `
- change := 0;+ l& X2 ]2 P6 A/ U9 n5 X
- else
$ x4 \4 X2 T" J) n$ a - change := 0;
3 ]) u6 p G5 Z" d: u - if WR_PTR'event then
' x& R0 j i7 [8 K9 |' W - change := 1;
& S5 s$ K, j% R7 H' n% H - end if;
5 F4 j) G) S% s( p3 }# q: H$ F - if RD_PTR'event then
+ x0 Y) n# n5 } o% W# p% V. s - change := change - 1;9 s. _$ ~+ ?. J2 K' p
- end if;
2 o' z w0 U C" {, ^) o7 \ - count <= count + change;
8 I8 _* R6 `+ W - end if;
* B# B |' N# b, S3 J- @' y$ X% ` - end process;
& n6 f9 W: H! O2 E* } - STATUS: process(count)& u1 R5 _6 L3 l, u2 `
- begin $ V- b3 f) [8 r5 w! X, |0 R
- if count=0 then
8 O$ R+ z: k: O% d - FULL <= '0';9 R% _' z! p) L
- EMPTY <= '1';
7 n& m" i4 P0 a, w" I' a" I/ Y+ @ - elsif count=depth then; Y W6 e3 ]- X2 E/ L$ t2 F7 w
- FULL <= '1';
?% ]) Z7 f1 Y9 J, m' y: _9 w - EMPTY <= '0'; 8 B& [8 s5 r) Y) d+ m
- else
# q4 ^8 Y( ^) @3 H - FULL <= '0';
- b# K X6 Y) d - EMPTY <= '0';
6 k# E/ t1 L% E0 A4 E/ L+ l! c - end if; ) F2 d9 J1 D- e
- end process;
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