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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。: o' n) l2 S8 W
//所有註解都要保留
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/ b; ]1 L4 F( d; x* B`timescale 1 ns / 1 ns
4 M# _4 T1 x' t& `2 d3 L! w8 \8 ?* imodule xclk(sclk,ena,set,outp);9 [* p$ e2 Z8 I) X7 _
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input sclk,ena;
; ?- U4 V3 D- G+ Ainput [1:0]set;, P: \7 y6 g8 ]) Q
output outp;
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wire outp;2 Q& q( V' ]9 Z2 e, `
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/**** Node preservation for nodeA **************/
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//exemplar attribute nodeA_5 preserve_signal true) _# g/ M7 L1 n) d
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//exemplar attribute nodeA_4 opt keep0 c- U$ M7 m- h/ s
/ T( B, @. s8 x- q+ q2 N6 L' Q/**** The following comment form also works ****/
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//exemplar attribute nodeA_3 preserve_signal true: k7 k ~ C1 h4 K7 m, d8 h! V: k
+ j) O4 {9 ~; d/ j, N4 `( M//exemplar attribute nodeA_3 opt keep
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8 L6 r \' W8 M3 A' d/**** The following comment form also works ****/1 d; R& `- J" i7 k8 S' E+ L; r
$ [, U! k# S, B' x# D6 b% s9 w//exemplar attribute nodeA_2 preserve_signal true
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//exemplar attribute nodeA_2 opt keep* T; S+ I* S7 N
, h% U* I: K0 o' H" ]1 Z" c1 m t0 A/ y/**** The following comment form also works ****/% U7 e' E z* k. N
/ c5 u# w# ]/ ~) I, Y//exemplar attribute nodeA_1 preserve_signal true g" d! A# |; t0 O# j( f5 G1 [) t
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//exemplar attribute nodeA_1 opt keep
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6 j s2 [$ p. i8 c3 U4 S/**** The following comment form also works ****/+ J1 E* B4 O9 v8 w+ l
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/*exemplar attribute nodeA_0 preserve_signal true$ O/ a$ _: d$ t+ T
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exemplar attribute nodeA_0 opt keep*/
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wire nodeA/* synthesis syn_keep=1 opt="keep"*/;
# h) Q) P2 j" T8 s% `; mwire nodeA_0/* synthesis syn_keep=1 opt="keep"*/;1 r0 D. _7 b3 e4 U0 |
wire nodeA_1/* synthesis syn_keep=1 opt="keep"*/;4 w- J: x9 ^' }3 v: l
wire nodeA_2/* synthesis syn_keep=1 opt="keep"*/;9 q+ }* ?" d F! ?
wire nodeA_3/* synthesis syn_keep=1 opt="keep"*/;
\9 ?* X0 \: y; e" H" V' o/ d5 |wire nodeA_4/* synthesis syn_keep=1 opt="keep"*/;
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, `* H7 ^1 q, _assign#1 nodeA_0 = sclk & ena;
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s8 d& C8 d% U$ i, ?assign#1 nodeA_1 = ~ nodeA_0;
. h6 e: ^, w: u" r5 E7 b0 Eassign#1 nodeA_2 = ~ nodeA_1;8 `5 j5 V# y" X8 W8 e% r
assign#1 nodeA_3 = ~ nodeA_2;: |: r! D2 f. n% z9 c
assign#1 nodeA_4 = ~ nodeA_3;
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reg xout;
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4 U8 j4 l2 }/ i( |. i- C& E9 salways@(nodeA_1,nodeA_2,nodeA_3,nodeA_4,set)' y S# s+ r. d2 R
casez(set): Q1 P+ \% V( X ^4 a9 y7 `
1: xout =#1 nodeA_2;9 ?3 T' E8 a& N7 r& x
2: xout =#1 nodeA_3;& e7 c5 F, [2 S8 s
3: xout =#1 nodeA_4;
* w: q6 b! Z* ^ default: xout =#1 nodeA_1;
+ c+ E, r% z/ v endcase
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3 p0 B+ p" U; t9 ^3 lassign#1 nodeA = xout;
7 S! N* ?/ a5 u# Zassign#1 outp = ena ? nodeA^sclk : 1'bz;
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' Z& \" `4 m* O7 Tendmodule
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`timescale 1 ns / 1 ns
3 \/ r. y) C9 Q; q+ bmodule xclk_tf();
$ V+ c: h' z S# K- a
) W a0 q6 z1 U' P2 N// Inputs
5 d" p4 k) W W7 l n- O$ R# M7 B' J reg sclk;7 |& s; i# S: Z9 \; \
reg ena;
2 H! x) v2 I) X% f reg [1:0] set;2 r1 S9 }( V* t6 ^4 x" _* \0 ]" l
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// Outputs1 l- ^4 e$ j4 J6 @9 g" J5 A2 S4 v4 A' z
wire outp;9 z' r% b q8 u" O& D2 G0 Z
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# S6 G: S, u3 K0 V1 W6 t+ ?' ~
xclk UUT (* @1 r/ |+ f8 k3 U9 U
.sclk(sclk),
, ]) S3 O8 F3 D6 D .ena(ena), : `& ~! D1 {/ g% P+ }. _+ l' f
.set(set),
2 j$ e) ]$ D7 B7 l! e .outp(outp)
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/ _+ h+ A4 ?# n8 u" q initial begin
' }% v# j; v4 w9 g8 i' J( m9 p sclk = 0;
. h1 ~6 J0 u$ q5 v# J8 f* j ena = 0;( s8 v4 }! Q& w
set = 0;
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always# 5 sclk = !sclk;, S2 J5 e0 ~& z8 a3 _! ]
# W) z# _# g, m d% A+ U2 w: [% z8 Vinitial begin
# c' B& t t! q* m! r: H #100
}8 \$ t' k. d, S ena = 1;
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set = 2;
4 l L) w/ J, W: R) R1 _ #2000 " \, }& o+ i* Z! p- a
set = 3;
0 Z: w6 e- Y2 o# i$ w8 N #2000+ s, O- w8 s$ f1 D( ~) z
$finish;( B! S# W$ J6 \" ], A8 J* _! W- S
end+ e9 F9 f4 X, F+ a
endmodule // xclk_tf |
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發表於 2007-6-10 21:50:08
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