📄 00866.html
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN">
<html>
<head>
<title>第十九章 接口</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', '00866.html');" onmousedown="onBodyMouseDown();">
<!-- Begin Popups -->
<div class="Element801" id="popup00397">
<div class="Element800">
<div class="Element14">
链接</div>
<div class="Element11">
<div class="Element10">
<a href="00957.html" target="topic">主题</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, 'popup00397');"><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="00202.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><img src="btn_up_d.gif" border="0" alt="Up" title="Up"><a href="00213.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">
第十九章 接口</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="主题"></a><div class="Element14">
<a onclick="toggleVisibilityStored('主题');" class="a_Element14"><img src="sectionminus.png" border="0" alt="" title="" id="img主题">主题</a></div>
<div id="div主题">
<div class="Element11">
<div class="Element10">
<div class="Element212">
<div class="TableDiv">
<table cellspacing="0" class="Table0">
<tr>
<td class="Element200" valign="top" width="50%">
<div class="Element201">
主题 </div></td><td class="Element204" valign="top" width="50%">
<div class="Element205">
描述 </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00213.html" target="topic">19.1 简介（一般信息）</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
The communication between blocks of a digital system is a critical area that can affect everything from ease of RTL coding, to hardware-software partitioning to performance analysis to bus implementation choices and protocol checking. The interface construct in SystemVerilog was specifically created to encapsulate the communication between blocks, allowing a smooth migration from abstract system-level design through successive refinement down to lower-level register-transfer and structural views of the design. By encapsulating the communication between blocks, the interface construct also facilitates design re-use. The inclusion of interface capabilities is one of the major advantages of SystemVerilog.<br><br>At its lowest level, an... <a href="00213.html" target="topic">more</a> </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00214.html" target="topic">19.2 接口语法</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
</div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00218.html" target="topic">19.3 接口中的端口</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
One limitation of simple interfaces is that the nets and variables declared within the interface are only used to connect to a port with the same nets and variables. To share an external net or variable, one that makes a connection from outside of the interface as well as forming a common connection to all module ports that instantiate the interface, an interface port declaration is required. The difference between nets or variables in the interface port list and other nets or variables within the interface is that only those in the port list can be connected externally by name... <a href="00218.html" target="topic">more</a> </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00219.html" target="topic">19.4 modport</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
To restrict interface access within a module, there are modport lists with directions declared within the interface. The keyword modport indicates that the directions are declared as if inside the module. </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00225.html" target="topic">19.5 接口与specify块</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
The specify block is used to describe various paths across a module and perform timing checks to ensure that events occurring at the module inputs satisfy the timing constraints of the device described by the module. The module paths are from module input ports to output ports and the timing checks are relative to the module inputs. The specify block refers to these ports as terminal descriptor. Module inout ports can function as either an input or output terminal. When one of the port instances is an interface, each signal in the interface becomes an available terminal, with the default... <a href="00225.html" target="topic">more</a> </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00226.html" target="topic">19.6 接口中的任务与函数</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
Tasks and functions can be defined within an interface, or they can be defined within one or more of the modules connected. This allows a more abstract level of modeling. For example “read” and “write” can be defined as tasks, without reference to any wires, and the master module can merely call these tasks. In a modport these tasks are declared as import tasks.<br><br>If a module is connected to a modport containing an exported task or function, and the module does not define that task or function, then an elaboration error shall occur. Similarly if the modport contains an... <a href="00226.html" target="topic">more</a> </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00231.html" target="topic">19.7 参数化接口</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
Interface definitions can take advantage of parameters and parameter redefinition, in the same manner as module definitions. This example shows how to use parameters in interface definitions. </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00232.html" target="topic">19.8 虚拟接口</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
Virtual interfaces provide a mechanism for separating abstract models and test programs from the actual signals that make up the design. A virtual interface allows the same subprogram to operate on different portions of a design, and to dynamically control the set of signals associated with the subprogram. Instead of referring to the actual set of signals directly, users are able to manipulate a set of virtual signals. Changes to the underlying design do not require the code using virtual interfaces to be re-written. By abstracting the connectivity and functionality of a set of blocks, virtual interfaces promote code-reuse.<br><br>A... <a href="00232.html" target="topic">more</a> </div></td></tr><tr>
<td class="Element202" valign="top" width="50%">
<div class="Element203">
<a href="00235.html" target="topic">19.9 对接口对象的访问</a> </div></td><td class="Element206" valign="top" width="50%">
<div class="Element207">
Access to all objects declared in an interface is always available by hierarchical reference, regardless of whether or not the interface is connected through a port. When an interface is connected with a modport in either the module header or port connection, access by port reference is limited to only those objects listed in the modport, for only those types of objects legal to be listed in modports (nets, variables, tasks, and functions) All objects are still visible by hierarchical reference. For example: </div></td></tr></table></div></div>
</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="00957.html" target="topic">主题</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 + -