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//可直接透過synthesis tool用於PLD，FPGA不可 LUT delay則要採其他方式。' U# ^# ~- \5 k
//所有註解都要保留3 N# [7 w8 l/ ], l( H
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`timescale 1 ns / 1 ns
% H- B% F" }$ S# ^: k! `+ Lmodule xclk(sclk,ena,set,outp);
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+ u' {# `2 o1 G4 \/ w- a {9 H& y# l0 A) x
* x- l2 A' U+ U$ Q3 k: ~8 oinput sclk,ena;
9 \9 w& l' }+ T* p P; o$ iinput [1:0]set;; R0 K2 [6 h' Q1 K/ U! \8 _! [
output outp; 6 i* M% u# R) O- u( w( t; b4 q3 k4 B
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wire outp;2 o% Y0 A6 _) d; @4 A1 Q; s
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6 s% ~8 J: H8 i# ?, Z/ G/**** Node preservation for nodeA **************/
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* u: A2 S; z# [, q//exemplar attribute nodeA_5 preserve_signal true
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//exemplar attribute nodeA_4 opt keep
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/**** The following comment form also works ****/5 Y7 V5 u& J5 r( l
3 J" ^* [/ d& z7 t//exemplar attribute nodeA_3 preserve_signal true
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5 i# A3 x1 \$ q, r( O7 l//exemplar attribute nodeA_3 opt keep% e+ F( q) G( m# c0 b% O9 h4 z A
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/**** The following comment form also works ****/9 F$ k1 t \4 C
" |; g" m$ ?& v0 @" M& I//exemplar attribute nodeA_2 preserve_signal true
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! m6 W6 N. p+ k6 _" y//exemplar attribute nodeA_2 opt keep' R. e9 |; y1 Z) V' L5 y9 t- e7 ]
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/**** The following comment form also works ****/
1 d/ P4 z5 [( S! L! i" o W$ C! e2 E8 Y2 ~& E( A
//exemplar attribute nodeA_1 preserve_signal true
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//exemplar attribute nodeA_1 opt keep. r$ ]+ z6 S5 c7 O2 z8 z& x; a
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5 Q/ X1 R. o* n- D+ Y! m! \/**** The following comment form also works ****/
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% x9 J( Y7 R2 a: J+ p; P/*exemplar attribute nodeA_0 preserve_signal true- L! {) c% O; B& D) c
8 L1 ~+ Y* s) K" A1 F) r
exemplar attribute nodeA_0 opt keep*/
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V( y; r1 W, [' J7 A$ T' f4 _ K
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wire nodeA/* synthesis syn_keep=1 opt="keep"*/;% n/ r% o% q, f. u
wire nodeA_0/* synthesis syn_keep=1 opt="keep"*/;% \- F# R2 i5 Y
wire nodeA_1/* synthesis syn_keep=1 opt="keep"*/;' ~8 W3 d, }0 c
wire nodeA_2/* synthesis syn_keep=1 opt="keep"*/; m( b7 y' D6 w! z# g* e2 |! D. z
wire nodeA_3/* synthesis syn_keep=1 opt="keep"*/;
% X! k1 Y* S& r1 Uwire nodeA_4/* synthesis syn_keep=1 opt="keep"*/;
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assign#1 nodeA_0 = sclk & ena;
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assign#1 nodeA_1 = ~ nodeA_0;% Z: A8 ? h% `2 Y; y8 U
assign#1 nodeA_2 = ~ nodeA_1;
! v( g* c! v3 B; {! H! fassign#1 nodeA_3 = ~ nodeA_2;2 f$ u8 h) Q% K* B/ W, Q$ V
assign#1 nodeA_4 = ~ nodeA_3;
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. M p: o8 F* ]reg xout;
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always@(nodeA_1,nodeA_2,nodeA_3,nodeA_4,set)! E; [; @$ i1 B) U" S
casez(set)( m# Z7 x7 X' _9 y* A& @6 F
1: xout =#1 nodeA_2;: y( V! {0 j( ]1 C. p6 V
2: xout =#1 nodeA_3;
% a: o/ q1 |, C4 n y/ X 3: xout =#1 nodeA_4;. G ?& o( o1 O2 q0 M3 r
default: xout =#1 nodeA_1;/ v( H2 T( f$ G# @1 Q7 r5 K$ h+ J; [( P
endcase. v! _( r3 M! F! O
% A: C R. F1 C- i- _
assign#1 nodeA = xout;6 O. B9 z' ?" a& B2 w: |9 O5 |
assign#1 outp = ena ? nodeA^sclk : 1'bz;
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+ M' q' ~9 s6 f3 b! ]endmodule
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`timescale 1 ns / 1 ns# e+ L. Z# k3 J' E$ f/ v0 P& P
module xclk_tf();
8 I3 e. C* u9 b$ g& ^5 _2 |
/ {- L" H" C2 F+ \// Inputs* U' M$ ?% u6 C3 _0 {
reg sclk;
* b% I0 m4 C9 Y6 D reg ena;2 F( K0 P' F) y6 H" n8 u* ?, \
reg [1:0] set;
% P7 A& O2 Q6 {. J0 b
2 k! U3 `: t5 M, b
7 x- F* c+ E9 Z1 d# k// Outputs
3 ?# n. q+ R) ^* j7 M wire outp;
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3 ]. A0 G1 T7 O0 I. e9 p; Y xclk UUT (; Q; c! _; @% L# S# Y" S5 ~. M" Q: B0 F
.sclk(sclk),
! x) L/ ~: p _1 h9 f+ z( ]3 H .ena(ena),
1 W/ [: G! N% ~5 t .set(set),
+ b7 _8 x8 P: J" F% L' P1 R .outp(outp)4 r& T) H4 M7 u7 Y
);
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$ i1 F9 c' [3 ]% R4 [! [9 n initial begin* ^6 \4 D- J/ z! P, ]
sclk = 0;
+ G0 z$ |& i0 g1 C2 A! I# ^! @* | ena = 0;+ f1 w( ~8 P$ E2 a5 G4 z
set = 0;
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always# 5 sclk = !sclk;
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& k2 w9 @ g+ w7 s# kinitial begin8 Q9 y+ W, {5 k, }+ {
#100
( r1 [; T2 L: g- W! X ena = 1;7 P' F% u! j+ K& _2 U' m3 b
#2000
+ }7 [( x5 _4 Y; B set = 2;
9 `7 J$ m i1 [% [# w& L5 f' |/ A) ^ #2000 2 Y6 T: S* Q7 X' n& P: q
set = 3;
2 d2 h# X6 A( T; u7 w! _ #2000% k. s7 l) M4 }8 ?" P+ N! M
$finish;3 q2 b6 h) w3 [2 [9 `( ] d
end
/ \. i2 ]1 y. i+ e0 b' v4 {) @0 _endmodule // xclk_tf |
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發表於 2007-3-17 11:29:24
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