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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。: ]+ s& E& R$ z0 H! Z0 I
//所有註解都要保留. V* z- |" L2 Z8 g( u% m" F
/ u' T" D4 X. e6 X6 o" ^`timescale 1 ns / 1 ns$ b# V) u% S! u
module xclk(sclk,ena,set,outp);
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3 E& d2 ~9 x r/ A+ e. a0 Cinput sclk,ena;, C% x& Y, e+ l+ _3 Y
input [1:0]set;# }1 n4 p3 k! Q* _* k% m
output outp;
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wire outp;
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/**** Node preservation for nodeA **************/: E7 @2 G5 v% L* G" {
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- f5 |) r* ?7 O# B//exemplar attribute nodeA_5 preserve_signal true- v, t: C/ }; `
A% C4 o, L2 V0 }+ R. {//exemplar attribute nodeA_4 opt keep! p+ H) E% |) g( x3 l* t+ b
0 A5 e' z7 K8 \& l0 e1 v/**** The following comment form also works ****/
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//exemplar attribute nodeA_3 preserve_signal true
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7 l1 b! L3 J) x. v//exemplar attribute nodeA_3 opt keep
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/**** The following comment form also works ****/
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! ?9 p' ]4 N; `: i% \6 j/ u//exemplar attribute nodeA_2 preserve_signal true/ C T$ }& Z3 i0 Q' A2 m
& z, Z z( w5 v* L, t7 v* m9 d$ |//exemplar attribute nodeA_2 opt keep2 k# E; C% f, b
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/**** The following comment form also works ****/
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//exemplar attribute nodeA_1 preserve_signal true# O% v3 ?$ l% B, s/ L$ J4 y0 A
8 u# e0 k( s: c0 V# E//exemplar attribute nodeA_1 opt keep# F! P3 K# T' k; y
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/**** The following comment form also works ****/. D/ w" L$ v, g M
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/*exemplar attribute nodeA_0 preserve_signal true8 j) P) E0 K" z( `( @5 T/ y! Z
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exemplar attribute nodeA_0 opt keep*/
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2 I0 t) Q. l3 C6 \, pwire nodeA/* synthesis syn_keep=1 opt="keep"*/; [7 j" `' p. c; i, j
wire nodeA_0/* synthesis syn_keep=1 opt="keep"*/;4 l2 a6 L) M% ]$ k
wire nodeA_1/* synthesis syn_keep=1 opt="keep"*/;) f8 ~, H5 e# x4 F: I
wire nodeA_2/* synthesis syn_keep=1 opt="keep"*/;* J) _2 \( S9 _$ E; M9 R4 `
wire nodeA_3/* synthesis syn_keep=1 opt="keep"*/;/ h$ U* s5 m6 Y K F
wire nodeA_4/* synthesis syn_keep=1 opt="keep"*/;
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assign#1 nodeA_0 = sclk & ena;
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! E8 X4 q& s5 O* C4 H! xassign#1 nodeA_1 = ~ nodeA_0;; u4 L- a4 R3 J
assign#1 nodeA_2 = ~ nodeA_1;6 U$ y, V5 |! f& R8 ?4 Y
assign#1 nodeA_3 = ~ nodeA_2;
# ^; z/ t9 z& S& l9 c8 g" T- \assign#1 nodeA_4 = ~ nodeA_3;( d; f# P4 O; F/ P
$ I, y: Z. R+ {8 ^3 B0 E9 Ereg xout;' L' h" g" h0 i/ [# A# a
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always@(nodeA_1,nodeA_2,nodeA_3,nodeA_4,set)3 b7 k$ q- [& g* {: p( T3 O
casez(set)
S, d' k. T+ W+ [+ E 1: xout =#1 nodeA_2;6 z9 ]( N- R h
2: xout =#1 nodeA_3;0 u9 B3 F$ L( L1 n, B6 g
3: xout =#1 nodeA_4;
! V0 T/ }+ R: l4 f default: xout =#1 nodeA_1;8 w3 @3 h- S" N* K2 E
endcase
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/ k: S0 w4 u5 z5 d A1 L& m% iassign#1 nodeA = xout;
8 A) M. P. [) F3 C% Y( l% O$ Dassign#1 outp = ena ? nodeA^sclk : 1'bz;
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- q% q; Y( _0 S% Xendmodule
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: R9 r( L- s1 M/ q# Z& B T4 R`timescale 1 ns / 1 ns0 z4 s I! d2 R: b9 F
module xclk_tf();1 Q* n* \; o1 U- _5 d! A1 f* K
- j; w; |( F2 l. ^0 o2 A. K/ S// Inputs
+ Q/ V H) f/ E: z/ d/ y+ B reg sclk;
' y+ ?& b, m" i9 l reg ena;; w/ H. k1 D' j8 F K5 U& O0 f
reg [1:0] set;, t; T; u3 ]2 `& `. |1 t, N
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) m) F9 V# R3 s% U ]3 S. H! s// Outputs
$ `, p$ [5 |2 V wire outp;
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xclk UUT (
# _( R7 N; i1 O, C2 K' d9 m/ H- c .sclk(sclk),
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0 I0 R$ _* F* ` .set(set),
$ W5 s* I! i* q7 w, [! ` .outp(outp)" g9 Y/ l5 d* J2 x
);
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initial begin
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ena = 0;
# d/ b j$ @; T4 K set = 0;
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4 y: z# z" ^ I( e. [ ialways# 5 sclk = !sclk;& S" I+ t: @) r( \3 w+ a+ z2 F
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initial begin
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ena = 1;" `- j2 m, Y1 E0 o+ u! n4 q; Y4 [
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set = 2;
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set = 3;
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$finish;
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endmodule // xclk_tf |
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