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根据前面对MCP3201芯片硬件和时序研究,设计如下FPGA 程序访问MCP3201
, J) p; p5 R6 d$ p5 N! ulibrary ieee;
3 H8 I+ }# S& M" R1 O; b% kuse ieee.std_logic_1164.all; 0 H: _9 C$ J. S5 u% q# T' K ?
use ieee.std_logic_arith.all;, n, r6 h+ L. y! J/ F0 ]" _
use ieee.std_logic_signed.all;# T8 F# |4 I' M! j8 C/ U% e/ H
entity get_ad_mcp3201 is+ s3 Y9 s* {, P" _
port
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clk: in std_logic; --------系统时钟20MHZ
0 Z7 M- Q x& o+ V7 k/ ` rst: in std_logic; --------低电平复位
& ^3 Y5 r8 [# ^# w+ M mcp3201_ncs: out std_logic;
1 ?5 N# i% D/ k/ a# u mcp3201_clk: out std_logic;
/ m/ M$ c& d; t$ S6 t0 m' |8 M8 }4 Q mcp3201_dout:in std_logic;9 _6 m4 G) A9 b9 h* u$ Z
mcp3201_ad_data: out std_logic_vector(11 downto 0)
2 x5 O& \" d# m S );
# M# X; F+ ^/ s1 y7 h0 A& T1 Eend get_ad_mcp3201; ^" k: z0 c, H* m1 h
architecture arch_get_ad_mcp3201 of get_ad_mcp3201 is
( f! [: H7 R0 ? R& X" {+ ~signal state : std_logic_vector(3 downto 0);/ |; Y2 ?1 f/ ~0 [. B0 h
signal clk_400k:std_logic;$ @2 L- k% _6 x& j) x
signal cnt: std_logic_vector(5 downto 0);
m' i% a3 V! Ssignal data_reg: std_logic_vector(11 downto 0);( ^( Z$ }; D3 Q! J0 x6 x
signal clk_period_num: std_logic_vector(4 downto 0);2 W: o/ u; i: M7 ?. P8 {
begin) m2 D' A( H2 I5 T" \$ S! U; i `
process(clk,rst)
8 S8 Q$ K0 o7 K2 ]begin
3 Z! Q' ]/ @5 x- j6 j' B, u, y0 d p4 zif (rst='0') then
' Z# U/ d- N& H/ W0 C1 ^ clk_400k<='0';* y" G6 F/ p) H3 n( m
cnt<=(others=>'0');* D0 q( ^7 r/ D: k$ s9 x
elsif clk'event and clk='1' then
; r9 P' c+ ^! T if (cnt="000000") then
9 u" D0 o+ c5 n% z7 t2 n# \7 } cnt<="110001"; ---495 h* O* } t9 l2 ?: I+ P9 v& }
clk_400k<='1';
0 t; H0 J. M1 q8 C! s2 w: y else% E) z/ w5 T8 N) c1 \- f
cnt<=cnt-"000001";
7 H( x" ]& z8 f4 T4 E end if;
; \# f. U3 e6 eend if; o$ }4 }8 t1 @ k6 e+ p# `
end process;9 P" y6 s. q- E8 [2 P
process(clk,rst)
; \5 ?0 c* X2 x: B& vbegin( s. ]+ q- E$ Z. ?4 ^; z
if (rst='0') then
9 _: N) O: j/ @; n, b mcp3201_ncs<='1';, d" k# v* r Y; i, S
mcp3201_clk<='0';) v6 }( m6 H- l7 z* _
mcp3201_ad_data<=(others=>'0');
$ {# Q8 K1 f) b# M( s. p clk_period_num<=(others=>'0');
" f( {. l$ N/ n) J* z: ^ data_reg<=(others=>'0');
4 W$ f6 \8 K% J4 l4 `8 q7 M state<=x"0";1 X k. w- f1 R# D4 c
elsif clk'event and clk='1' then
- D$ H$ K. S4 x if (clk_400k='1') then
9 B6 Q q( B( I3 T0 a! Y if (state=x"0") then, [9 L: y- ]% Z. |& [. d5 d
mcp3201_ncs<='1';
' @ G2 q( N/ m/ B state<=x"1";
8 f3 c6 z6 {% M elsif (state=x"1") then L+ u8 V! }! i5 X* i
mcp3201_ncs<='0';
% @8 e+ A& A; W mcp3201_clk<='0';8 a K$ |! M6 t
state<=x"2";
$ ^) z8 w; ?) V+ N( x( F1 H elsif (state=x"2") then
w+ {$ }, t O: r/ B. n# H G2 M mcp3201_clk<='1';
0 O# I$ a5 Y! g K if (clk_period_num="01110") then+ t' P- b. z9 Q J! G
clk_period_num<=(others=>'0');
3 G% d" u* D8 N8 i0 t r$ y1 C state<=x"3";
* D" L2 o5 Y3 J else; c( j# V& q9 @. W l& [8 o
clk_period_num<=clk_period_num+"00001";
- K* |0 T( N* ^. g, @ state<=x"1";
) x! d) e: \9 ?3 }+ c1 T end if;- `* O% q7 B! K3 ]0 u6 S
if (clk_period_num>="00011") then
! `# z# x' }6 k1 o data_reg<=data_reg(11 downto 1) & mcp3201_dout;
* ~0 z- A9 [) ?! z+ `, E end if;! x; F j+ g% x/ e/ Q3 d3 A- ]
" K# v+ J- | g5 R' v6 L+ Y! _
elsif (state=x"3") then
; j. g) U* ]1 m! G5 i w mcp3201_ncs<='1';
' j# U8 P4 b7 m state<=x"0";
2 q8 ?+ B N O mcp3201_ad_data<=data_reg;+ B( i5 q( m% S6 p# y1 P i, h, V% s
else; T0 q) W) t: P9 t: {+ A# j6 j* ~$ C
mcp3201_ncs<='1';
, R' N" ? [4 K( ~* v. c state<=x"0";
0 n0 t, A7 ?: [7 t/ S% e7 L end if ;2 w0 \7 N9 l# a% s) R! G7 L
end if;/ b! v+ p2 U6 k, [7 R! U
end if;
: v3 e6 s5 D7 e9 x; P1 h' _$ ?end process;' H; v. v! T6 R6 _# D8 i
end arch_get_ad_mcp3201;
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