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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。- n5 A! h& l$ M( Y/ `+ F( J( ?) b
//所有註解都要保留5 s- C6 o7 @: _1 [* B3 E8 @7 a* t5 J
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`timescale 1 ns / 1 ns
& i" V1 R! ]" y7 [1 Q' E4 d7 nmodule xclk(sclk,ena,set,outp);! P% |! F8 y$ x6 J$ S0 m) K
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input sclk,ena;
, e5 `7 a: a7 f! X7 @/ h' Minput [1:0]set;
, h; B7 i' e3 P: T. B1 Soutput outp;
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9 i i2 G' |9 @6 \6 b+ T/ twire outp;
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+ T% f) N: Z8 J7 h% N3 G/**** Node preservation for nodeA **************/ a+ {; ~8 A, [& F
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//exemplar attribute nodeA_5 preserve_signal true6 [! |! p& @2 L# i- n- u4 v8 {1 k
8 f. |1 E2 w1 g5 w% ]) K h2 d) w }//exemplar attribute nodeA_4 opt keep
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. N; y% k6 I; P5 N2 T6 F2 A/**** The following comment form also works ****/; Z5 r% s& n) ]/ X @& h1 B& G e& {( F
# q# h; }; ~" q# Y//exemplar attribute nodeA_3 preserve_signal true" \) O! z5 N/ g6 _; l& q! L6 q" ]
0 u3 y) w2 b7 T |, g, G0 N+ w//exemplar attribute nodeA_3 opt keep
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$ v( l- k6 ^0 K; s/ A& r/**** The following comment form also works ****/6 s+ x' H1 [, R/ Y8 Z5 i9 c
/ n4 F, k# a! T$ ~- ]; J//exemplar attribute nodeA_2 preserve_signal true
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& m% ^: o/ D. u+ E//exemplar attribute nodeA_2 opt keep% {) z0 J' `$ V
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/**** The following comment form also works ****/# J. D0 q% ^' h1 Q2 p/ u
0 x( \9 t- O# _1 D//exemplar attribute nodeA_1 preserve_signal true
1 @( k& {" D* R/ B0 p
* M( A1 X9 W, V//exemplar attribute nodeA_1 opt keep
% s1 C9 Q- e, e9 H8 f7 I % |$ a( Y" N) Q- {1 P
! [: _) n, w+ y/**** The following comment form also works ****/' I) K- z1 E# X' S1 v9 s2 d
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/*exemplar attribute nodeA_0 preserve_signal true
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exemplar attribute nodeA_0 opt keep*/
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' Z; o( z. R. _6 ewire nodeA/* synthesis syn_keep=1 opt="keep"*/; L. H0 X3 y9 x0 [: t
wire nodeA_0/* synthesis syn_keep=1 opt="keep"*/;' y' l' ~) W: Q8 {) x
wire nodeA_1/* synthesis syn_keep=1 opt="keep"*/;
! k" O/ L; e' {# `/ _7 owire nodeA_2/* synthesis syn_keep=1 opt="keep"*/;
' N" B, Z2 Q( l6 Pwire nodeA_3/* synthesis syn_keep=1 opt="keep"*/;6 g4 T0 k$ w, B1 k
wire nodeA_4/* synthesis syn_keep=1 opt="keep"*/;
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assign#1 nodeA_0 = sclk & ena;
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# V! l" A; \! m' Massign#1 nodeA_1 = ~ nodeA_0;3 r6 F: ?$ q) ^- \% f. j
assign#1 nodeA_2 = ~ nodeA_1;
6 q0 K% b* @* V {: X, K1 C3 Dassign#1 nodeA_3 = ~ nodeA_2;& i2 E, Z# a/ Z
assign#1 nodeA_4 = ~ nodeA_3;2 o1 ?( e# k/ x3 C4 M
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reg xout;) u0 f0 m" J" w; w: M( L
; o+ [9 u4 J- Xalways@(nodeA_1,nodeA_2,nodeA_3,nodeA_4,set)
) ]3 u U. q1 ^) } @& _ casez(set)) X/ S0 B( c: i9 J
1: xout =#1 nodeA_2;
. V7 }" y( R9 p 2: xout =#1 nodeA_3;7 l6 F( Y. t3 h- R+ G, ]2 G
3: xout =#1 nodeA_4;
2 s+ S/ f- H. W) P2 T, k9 C default: xout =#1 nodeA_1;
1 ^! C. |- O9 _9 r" |" A endcase
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assign#1 nodeA = xout;
0 r, [ Z2 M! ^7 L' f# [; M6 xassign#1 outp = ena ? nodeA^sclk : 1'bz;! x" T5 K3 L8 Z& [! D
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endmodule
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( H C% B% v8 d z* e* @1 k1 x`timescale 1 ns / 1 ns
1 Q1 {: V$ B7 y& {5 Z1 {8 g3 G$ bmodule xclk_tf();3 d" s( |8 F) T, X4 z
2 Z7 X1 z# o6 b// Inputs: `8 J. d3 M' R6 c
reg sclk;
0 q, J0 U) @; D& C8 P+ w3 u9 U reg ena; Y1 e: f! z0 P1 F
reg [1:0] set;
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// Outputs
8 M a a8 l! e. d) z wire outp;2 `# t! e# \% N U+ V( c: \( n
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xclk UUT (0 F& w% w% [' E! e7 z
.sclk(sclk), 0 C* Q, [% i9 V5 E! p/ @3 R# m3 m) U# S
.ena(ena),
' P7 p% n0 E6 z& B3 ` .set(set), ' u* i1 }4 E( x8 r; ]& K r
.outp(outp)
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initial begin( u. o& x1 U% n( |. I3 B5 u
sclk = 0;" v6 V6 p6 b) j$ D& J6 W# ^6 ^
ena = 0;9 C* d2 I# Z- w, D( k4 n, d
set = 0;
! p% I# K% i/ H( k7 r4 c end
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always# 5 sclk = !sclk;9 b. Q+ _! V" k6 i
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initial begin# O! |% m$ M' D1 W' ?3 L0 n, [4 N2 i
#100
`+ C! ~3 h6 A# l% x+ Z7 y+ p ena = 1;& d/ a- I' j' K9 [
#2000
1 D- }! @7 J# e( [) E: f set = 2;
' ?0 M4 p) p! G9 w #2000
8 z7 L9 Y, A' w7 j2 T. m9 q set = 3;0 _, S. X6 _' r2 }* H
#2000
4 K: o/ \6 r4 c7 ^ Q; Y $finish;: ?4 @" J8 e+ x& t+ T
end7 Y1 F! {- T/ U- Q- e- @; h
endmodule // xclk_tf |
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發表於 2007-3-17 11:29:24
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