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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。
% @2 J' h8 g0 S" z//所有註解都要保留0 k2 @7 B. r- X# U t# E
. ^" v' T7 D2 I$ z`timescale 1 ns / 1 ns
/ w6 z$ X3 }; `+ l+ ?module xclk(sclk,ena,set,outp);
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$ Y& S6 G Y, o- kinput sclk,ena;
8 h- \2 f7 m- Q2 p- f% Hinput [1:0]set;2 w' n6 I F* }- D
output outp;
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7 j" y# l% ? c! d+ D3 Dwire outp;( g! W8 `( U) R4 M7 i5 ?! M
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5 V6 d4 k' D9 o/**** Node preservation for nodeA **************/
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//exemplar attribute nodeA_5 preserve_signal true8 f, ^: L, N* ]: Y# d# M' w& n
6 Y/ \. D" m# d7 F k) D//exemplar attribute nodeA_4 opt keep
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8 j: r1 p9 B7 ^/**** The following comment form also works ****/% t# O: T% X2 K, k
$ k) S3 ~! a. D. m//exemplar attribute nodeA_3 preserve_signal true
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& [3 U1 i- R' X! k, r# }7 q//exemplar attribute nodeA_3 opt keep- S+ i; @( g4 c/ l7 X
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/**** The following comment form also works ****/9 i4 f# D% e8 X+ G
! W/ ]# g1 ^8 j! L+ t//exemplar attribute nodeA_2 preserve_signal true
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//exemplar attribute nodeA_2 opt keep, A" H% y4 \4 ~% M+ H
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/**** The following comment form also works ****/
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" v( W, H, ]5 S4 L( U4 B) b, {//exemplar attribute nodeA_1 preserve_signal true
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//exemplar attribute nodeA_1 opt keep
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* c* ~, L4 |8 ]7 x+ d* ?/**** The following comment form also works ****/
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/*exemplar attribute nodeA_0 preserve_signal true
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exemplar attribute nodeA_0 opt keep*/ 2 J w$ G. Q* c
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wire nodeA/* synthesis syn_keep=1 opt="keep"*/;3 G- H/ {( S0 l8 ^1 \1 m( K, A
wire nodeA_0/* synthesis syn_keep=1 opt="keep"*/;
, ~9 n3 F# W+ W# zwire nodeA_1/* synthesis syn_keep=1 opt="keep"*/;
' l w3 o, B- k$ [' S: dwire nodeA_2/* synthesis syn_keep=1 opt="keep"*/;) Y2 K1 X9 z& R8 b5 ~1 Z1 Z
wire nodeA_3/* synthesis syn_keep=1 opt="keep"*/;7 R6 r$ M, Z2 e* G9 v8 R
wire nodeA_4/* synthesis syn_keep=1 opt="keep"*/;
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assign#1 nodeA_0 = sclk & ena;
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/ {! ^. M* r9 {$ j$ r2 r6 S% cassign#1 nodeA_1 = ~ nodeA_0;- N& B! A7 X1 d: {6 b% _: C4 ?# r
assign#1 nodeA_2 = ~ nodeA_1;
, N% ^5 n4 q8 q2 s L1 Uassign#1 nodeA_3 = ~ nodeA_2;' `0 m! |0 H$ j4 v
assign#1 nodeA_4 = ~ nodeA_3;
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; F* ?+ k, s' T, _7 r+ g6 `: Sreg xout;
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! d' ~" J9 W3 M! ]8 Valways@(nodeA_1,nodeA_2,nodeA_3,nodeA_4,set)
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1: xout =#1 nodeA_2;. C# M, n8 V( H
2: xout =#1 nodeA_3;
3 [! i- p* F( o1 J 3: xout =#1 nodeA_4;
( {/ } l- Q: k4 ?: r; y1 W6 O default: xout =#1 nodeA_1;' ?2 T3 e% h# Z$ u& D0 M& a
endcase ^- K1 `9 ~, P- q
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assign#1 nodeA = xout;, A6 g f7 b L1 R) x9 ~& z
assign#1 outp = ena ? nodeA^sclk : 1'bz;
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- Z& r/ W. w6 D7 ^5 h" R0 Z* dendmodule
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`timescale 1 ns / 1 ns
4 H& h- c% G. Q. e/ imodule xclk_tf();
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// Inputs$ N! s' x; g* o3 k
reg sclk;
# \& w* U1 o; d, r$ R4 c5 G" i- ~ reg ena;( ~- N' E; r$ P. j: h$ C
reg [1:0] set; K- m2 t1 E% r B9 D
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// Outputs4 b' Z# b9 ~9 m6 P
wire outp;, Q! L; Z0 S7 t/ x* N1 j8 h: V% a
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5 X" w; k8 ^( ]! e xclk UUT (9 ^; n4 h' d" S j! r* t. y
.sclk(sclk),
4 O l/ O) T# y' L7 L9 X0 y: j .ena(ena),
# e& Q+ v7 o$ w* c .set(set),
3 j( o2 @" {: \/ ^ .outp(outp)
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initial begin1 Q- W& W$ I/ N: p4 G" T
sclk = 0;+ z0 O ~) I' D& P
ena = 0;$ m* b/ h1 @2 d
set = 0;/ v; V' E9 j- {5 A
end
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always# 5 sclk = !sclk;
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initial begin
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ena = 1;8 T& C! @8 r$ W; o
#2000
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#2000
* x0 x/ O* ^" o9 ]& o' t' R8 K set = 3;- q8 y% q8 D: ~
#2000
0 J4 ]5 ~2 U+ U$ Y' J9 r0 l+ a( z $finish;3 j" M: [7 O" E' @
end
. z; L- l* @# w! h1 i x* Dendmodule // xclk_tf |
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