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8.10.1 序列事件</div>
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事件表达式中可以使用一个序列实例，它基于序列的成功匹配来控制过程语句的执行。这就允许命名序列的终点能够触发其它进程中的多个动作。<a href="00173.html" target="topic">语法17-2</a>和<a href="00174.html" target="topic">语法17-4</a>描述了声明命名序列和序列实例的语法。正像<a href="00577.html" target="topic">语法8-9</a>所显示的那样，一个序列实例可以直接使用在事件表达式中。 </p>
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当一个事件表达式中指定了一个序列实例的时候，执行事件控制的进程应该阻塞直到指定的序列到达终点。只要整个序列形成匹配，一个序列就到达终点。进程继续执行之后的检测到终点的Observe区域。 </p>
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使用一个序列作为事件控制的例子如下： </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00296"><pre class="Element12"><span style="color: #0000FF">sequence</span> abc<span style="color: #800080">;</span>
<span style="color: #800080">@(</span><span style="color: #0000FF">posedge</span> clk<span style="color: #800080">)</span> a <span style="color: #800080">##</span><span style="color: #FF0000">1</span> b <span style="color: #800080">##</span><span style="color: #FF0000">1</span> c<span style="color: #800080">;</span>
<span style="color: #0000FF">endsequence</span>
<span style="color: #0000FF">program</span> test<span style="color: #800080">;</span>
<span style="color: #0000FF">initial begin</span>
<span style="color: #800080">@</span>abc <span style="color: #0000FF">$display</span><span style="color: #800080">(</span><span style="color: #575D94">"Saw a-b-c"</span><span style="color: #800080">);</span>
L1 <span style="color: #800080">:</span> ...
<span style="color: #0000FF"> end</span>
<span style="color: #0000FF">endprogram</span></pre></div></div>
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在上面的例子中，当命名序列<i>abc</i>到达终点时，<span style="color: #0000FF">program</span>块<i>test</i>中的<span style="color: #0000FF">initial</span>块被解除阻塞，然后它显示字符串<span style="color: #575D94">"Saw a-b-c"</span>，并执行标记为<i>L1</i>的语句。在这个例子中，序列终点的作用是解除事件阻塞的触发器。 </p>
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使用在事件控制中的序列被实例化（就好像被一个断言特性语句实例化一样）；事件控制被用来同步序列的终点，而不管它的起始时间如何。序列的自变量应该是静态的；将自动变量作为序列的自变量会导致一个错误。</p></div>
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