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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。9 U+ q/ t: I2 o5 g) T
//所有註解都要保留& x- c, ?. P) X6 x- d
* p% g |5 A. u: Q* y: U# A`timescale 1 ns / 1 ns
" ^' ]8 m0 d; R1 umodule xclk(sclk,ena,set,outp);
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input sclk,ena;
$ @6 a5 G3 y. E- x C: Q) t9 Cinput [1:0]set;
$ z* e' l) U6 ^output outp; 1 ?3 h7 O+ K4 B: A) W
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wire outp;
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/**** Node preservation for nodeA **************/
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//exemplar attribute nodeA_5 preserve_signal true
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. K' b$ b$ P; g6 J- N/ j4 P//exemplar attribute nodeA_4 opt keep
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/**** The following comment form also works ****/3 I) y: |$ p0 C: C
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//exemplar attribute nodeA_3 preserve_signal true
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//exemplar attribute nodeA_3 opt keep/ R% b/ T( I8 \$ Y
' z% `$ r" S9 b( I* x& l/**** The following comment form also works ****/
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//exemplar attribute nodeA_2 preserve_signal true) k# y* R0 o5 @% C$ f( w/ T
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//exemplar attribute nodeA_2 opt keep9 J$ L3 O7 J9 g
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/**** The following comment form also works ****/
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; X8 }$ Y# n3 o% M7 C t; f//exemplar attribute nodeA_1 preserve_signal true
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//exemplar attribute nodeA_1 opt keep; b8 Z0 B! l6 n; l3 c F0 [
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/**** The following comment form also works ****/
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1 g- O0 e) i: ~! a% S2 [/*exemplar attribute nodeA_0 preserve_signal true
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0 Q/ r1 j6 | i. Z; U6 Rexemplar attribute nodeA_0 opt keep*/ / T& d5 a: Z* [& c3 j. P
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wire nodeA/* synthesis syn_keep=1 opt="keep"*/;
1 r& l ~7 I* ]wire nodeA_0/* synthesis syn_keep=1 opt="keep"*/;
$ J% H$ D% ~/ }8 c5 i, v& d$ L9 \wire nodeA_1/* synthesis syn_keep=1 opt="keep"*/;
" ^ r; @5 y% n0 ]; U: ^! H- ]wire nodeA_2/* synthesis syn_keep=1 opt="keep"*/; n8 N- X4 @, B4 s
wire nodeA_3/* synthesis syn_keep=1 opt="keep"*/;
7 g2 E8 ?; h6 S6 Fwire nodeA_4/* synthesis syn_keep=1 opt="keep"*/;
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assign#1 nodeA_0 = sclk & ena;' r4 g- J# ?- r1 B( L" r3 A
+ n p; {9 s- l; q8 P; ^2 Yassign#1 nodeA_1 = ~ nodeA_0;
8 i1 c& y& j, j- k% y* Oassign#1 nodeA_2 = ~ nodeA_1;" I' U* H) Z" V3 Z1 H
assign#1 nodeA_3 = ~ nodeA_2;. ]/ J) _) ?8 F& [) J9 T
assign#1 nodeA_4 = ~ nodeA_3;5 C7 ^! u3 `* L
( ], }3 S6 f6 e8 Lreg xout;9 O/ G: K" ~1 k! M& M; \
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always@(nodeA_1,nodeA_2,nodeA_3,nodeA_4,set)
# g c. T/ [( w* B) h casez(set)) {2 |0 @- N4 P/ H( t
1: xout =#1 nodeA_2;
8 N* O( r( e0 j; U& Y+ m 2: xout =#1 nodeA_3;0 m/ n* U2 C) ?6 m, d0 `
3: xout =#1 nodeA_4;
9 v3 l' z; B9 A0 K- k! c default: xout =#1 nodeA_1;- s+ L$ z" b# {. |& b
endcase3 ^- G5 S/ a( d/ }- u
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assign#1 nodeA = xout;' J& l4 x& [1 e- |- h
assign#1 outp = ena ? nodeA^sclk : 1'bz;. I& M6 y" H( Z- r9 N0 z6 P
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endmodule
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`timescale 1 ns / 1 ns I6 r1 \5 F; B6 e
module xclk_tf();
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// Inputs) f# {8 o! U' z& ^6 U
reg sclk;& t# B6 m! C2 J) ?
reg ena;
* z% l- C: E9 F5 ?& p% }2 Q1 r reg [1:0] set;: M6 n0 U8 q; k6 Z0 R
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' m/ y: L' K( W B s// Outputs7 E$ s6 F2 B0 g' p% V6 }
wire outp;
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xclk UUT (
7 a" V0 X- @% k& P; G4 B) h! b7 X .sclk(sclk),
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.outp(outp)
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initial begin
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always# 5 sclk = !sclk;8 |% y" ~: W; b( w( j h0 k
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initial begin
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ena = 1;8 s8 t0 g( n0 d% S
#2000
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set = 3;1 v$ B! V( G( D7 f
#2000
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end
* v/ \: z0 `7 O6 pendmodule // xclk_tf |
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