📄 00210.html
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN">
<html>
<head>
<title>18.7 外部模块</title>
<meta http-equiv="Content-Type" content="text/html; charset=GB2312" />
<meta name="generator" content="Doc-O-Matic" />
<meta http-equiv="Content-Style-Type" content="text/css" />
<link rel="STYLESHEET" href="default.css" type="text/css" />
<script type="text/javascript" src="scripts.js"></script>
</head>
<body class="Element700" onload="onBodyLoadEx('systemverilog31a.html', 'topic', '00210.html');" onmousedown="onBodyMouseDown();">
<!-- Begin Popups -->
<div class="Element801" id="popup00380">
<div class="Element800">
<div class="Element14">
链接</div>
<div class="Element11">
<div class="Element10">
<a href="00864.html" target="topic">第十八章 层次</a></div>
</div>
</div>
</div>
<!-- End Popups -->
<!-- Begin Page Header -->
<div class="Element710" id="areafixed">
<div class="Element92">
<table width="100%" cellspacing="0" cellpadding="0">
<tr><td width="33%">
<div class="Element1">
<a href="#" onmousedown="showPopup(this, 'popup00380');"><img src="seealsolink.png" border="0" alt="" title=""></a> SystemVerilog 3.1a语言参考手册</div>
</td><td width="34%">
<div class="Element2">
</div>
</td><td width="33%">
<div class="Element90">
<a href="00209.html" target="topic"><img src="btn_prev_lightblue.gif" border="0" alt="Previous" title="Previous" onmouseover="switchImage(this, 'btn_prev_lightblue_hover.gif');" onmouseout="switchImage(this, 'btn_prev_lightblue.gif');"></a><a href="00864.html" target="topic"><img src="btn_up_lightblue.gif" border="0" alt="Up" title="Up" onmouseover="switchImage(this, 'btn_up_lightblue_hover.gif');" onmouseout="switchImage(this, 'btn_up_lightblue.gif');"></a><a href="00211.html" target="topic"><img src="btn_next_lightblue.gif" border="0" alt="Next" title="Next" onmouseover="switchImage(this, 'btn_next_lightblue_hover.gif');" onmouseout="switchImage(this, 'btn_next_lightblue.gif');"></a></div>
</td></tr></table><div class="Element5">
18.7 外部模块</div>
</div>
</div>
<!-- End Page Header -->
<!-- Begin Client Area -->
<div class="Element720" id="areascroll">
<div class="Element721">
<!-- Begin Page Content -->
<div class="Element58">
<a name="描述"></a><div class="Element11">
<div class="Element10">
<p class="Element10">
To support separate compilation, extern declarations of a module can be used to declare the ports on a module without defining the module itself. An extern module declaration consists of the keyword extern followed by the module name and the list of ports for the module. Both list of ports syntax (possibly with parameters), and original Verilog style port declarations can be used. Note that the potential existence of defparams precludes the checking of the port connection information prior to elaboration time even for list of ports style declarations. </p>
<p class="Element10">
</p>
<p class="Element10">
The following example demonstrates the usage of extern module declarations. </p><div class="Element170">
<a href="#" onclick="CopyElementToClipboard('code00806');">Copy Code</a></div>
<div class="Element13"><div class="Element12" id="code00806"><pre class="Element12">extern module m (a,b,c,d);
extern module a #(parameter size= 8, parameter type TP = logic [7:0])
(input [size:0] a, output TP b);
module top ();
wire [8:0] a;
logic [7:0] b;
m m (.*);
a a (.*);
endmodule</pre></div></div>
<p class="Element10">
Modules m and a are then assumed to be instantiated as: </p><div class="Element170">
<a href="#" onclick="CopyElementToClipboard('code00807');">Copy Code</a></div>
<div class="Element13"><div class="Element12" id="code00807"><pre class="Element12">module top ();
m m (a,b,c,d);
a a (a,b);
endmodule</pre></div></div>
<p class="Element10">
If an extern declaration exists for a module, it is possible to use .* as the ports of the module. This usage shall be equivalent to placing the ports (and possibly parameters) of the extern declaration on the module. </p>
<p class="Element10">
</p>
<p class="Element10">
For example, </p><div class="Element170">
<a href="#" onclick="CopyElementToClipboard('code00808');">Copy Code</a></div>
<div class="Element13"><div class="Element12" id="code00808"><pre class="Element12">extern module m (a,b,c,d);
extern module a #(parameter size = 8, parameter type TP = logic [7:0])
(input [size:0] a, output TP b);
module m (.*);
input a,b,c;
output d;
endmodule
module a (.*);
...
endmodule</pre></div></div>
<p class="Element10">
is equivalent to writing: </p><div class="Element170">
<a href="#" onclick="CopyElementToClipboard('code00809');">Copy Code</a></div>
<div class="Element13"><div class="Element12" id="code00809"><pre class="Element12">module m (a,b,c,d);
input a,b,c;
output d;
endmodule
module a #(parameter size = 8, parameter type TP = logic [7:0])
(input [size:0] a, output TP b);
...
endmodule</pre></div></div>
<p class="Element10">
Extern module declarations can appear at any level of the instantiation hierarchy, but are visible only within the level of hierarchy in which they are declared. It shall be an error for the module definition to not exactly match the extern module declaration.</p></div>
</div>
<a name="Group"></a><div class="Element14">
<a onclick="toggleVisibilityStored('Group');" class="a_Element14"><img src="sectionminus.png" border="0" alt="" title="" id="imgGroup">Group</a></div>
<div id="divGroup">
<div class="Element11">
<div class="Element10">
<p class="Element10">
<a href="00864.html" target="topic">第十八章 层次</a></p></div>
</div>
</div>
<a name="Links"></a><div class="Element14">
<a onclick="toggleVisibilityStored('链接');" class="a_Element14"><img src="sectionminus.png" border="0" alt="" title="" id="img链接">链接</a></div>
<div id="div链接">
<div class="Element11">
<div class="Element10">
<a href="00864.html" target="topic">第十八章 层次</a></div>
</div>
</div>
</div>
<!-- End Page Content -->
<!-- Begin Page Footer -->
<hr width="98%" align="center" size="1" color="#CCCCCC" />
<table align="center" cellpadding="0" cellspacing="0" border="0">
<tbody>
<tr height="10">
<td></td>
</tr>
<tr align="center">
<td>
<script type="text/javascript"><!--
google_ad_client = "pub-5266859600380184";
google_ad_width = 468;
google_ad_height = 60;
google_ad_format = "468x60_as";
google_ad_type = "text_image";
google_ad_channel ="";
google_page_url = document.location;
//--></script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
</td>
</tr>
<tr height="15">
<td></td>
</tr>
<tr align="center">
<td>
<font size=2>除非特别声明，原文版权归作者所有，如有转摘请注明原作者以及译者（<a href="http://www.fpgatech.net/" target="_blank">FPGA技术网</a>）信息。<br />
如果您对本主题有何建议或意见，请登陆<a href="http://www.fpgatech.net/forum/forumdisplay.php?fid=18" target="_blank">FPGA开发者家园</a>提交，您的参与是我们前进的动力。</font>
<script language="javascript" type="text/javascript" src="http://js.users.51.la/195685.js"></script>
<noscript><a href="http://www.51.la/?195685" target="_blank"><img alt="我要啦免费统计" src="http://img.users.51.la/195685.asp" style="border:none" /></a></noscript>
</td>
</tr>
</tbody>
</table>
<!-- End Page Footer -->
</div>
</div>
<!-- End Client Area -->
</body></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -