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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML EXPERIMENTAL 970324//EN"><HTML><HEAD><META NAME="GENERATOR" CONTENT="Adobe FrameMaker 5.5/HTML Export Filter"><LINK REL="STYLESHEET" HREF="ch16.css"><TITLE> 16.5 `include</TITLE></HEAD><BODY BGCOLOR="#ffffff"><DIV><HR><P><A HREF="ch16.htm">Chapter start</A> <A HREF="ch16.4.htm">Previous page</A> <A HREF="ch16.6.htm">Next page</A></P></DIV><H1 CLASS="Section"><A NAME="pgfId=269"> </A>16.5 <A NAME="53338"> </A>`include</H1><P CLASS="Body"><A NAME="pgfId=270"> </A>The file inclusion (<B CLASS="Keyword">`include</B>) compiler directive is used to insert the entire contents of a source file in another file during compilation. The result is as though the contents of the included source file appear in place of the <B CLASS="Keyword">`include </B>compiler directive. The <B CLASS="Keyword">`include</B> compiler directive can be used to include global or commonly used definitions and tasks without encapsulating repeated code within module boundaries. </P><P CLASS="Body"><A NAME="pgfId=272"> </A>Advantages of using the <B CLASS="Keyword">`include</B> compiler directive include the following:</P><UL><LI CLASS="DashedList"><A NAME="pgfId=282"> </A>providing an integral part of configuration management</LI><LI CLASS="DashedList"><A NAME="pgfId=284"> </A>improving the organization of Verilog HDL source descriptions</LI><LI CLASS="DashedList"><A NAME="pgfId=287"> </A>facilitating the maintenance of Verilog HDL source descriptions</LI></UL><P CLASS="Body"><A NAME="pgfId=289"> </A>The syntax for the <B CLASS="Keyword">`include</B> compiler directive is as follows:</P><PRE CLASS="BNFDef"><A NAME="pgfId=290"> </A><CODE CLASS="code"> </CODE><B CLASS="Keyword">`include</B><CODE CLASS="code"> "</CODE><I CLASS="Emphasis">filename</I><CODE CLASS="code">"</CODE></PRE><P CLASS="Body"><A NAME="pgfId=291"> </A>The compiler directive <B CLASS="Keyword">`include</B> can be specified anywhere within the Verilog HDL description. The <I CLASS="Emphasis">filename</I> is the name of the file to be included in the source file. The <I CLASS="Emphasis">filename</I> can be a full or relative path name.</P><P CLASS="Body"><A NAME="pgfId=145"> </A>Only white space or a comment may appear on the same line as the <B CLASS="Keyword">`include</B> compiler directive. </P><P CLASS="Body"><A NAME="pgfId=296"> </A>A file included in the source using <B CLASS="Keyword">`include</B> compiler directive may contain other <B CLASS="Keyword">`include</B> compiler directives. The number of nesting levels for included files shall be finite.</P><P CLASS="Body"><A NAME="pgfId=146"> </A>Examples:</P><P CLASS="Body"><A NAME="pgfId=300"> </A>Examples of legal comments for the <B CLASS="Keyword">`include</B> compiler directive are as follows:</P><PRE CLASS="CodeIndent"><A NAME="pgfId=292"> </A><B CLASS="Keyword">`include</B><CODE CLASS="code"> "parts/count.v"</CODE></PRE><PRE CLASS="CodeIndent"><A NAME="pgfId=294"> </A><B CLASS="Keyword">`include</B> "fileB"<B CLASS="Keyword">`include</B> "fileB" // including fileB</PRE><P CLASS="Note"><A NAME="pgfId=295"> </A>NOTE--<A NAME="Include"> </A>Implementations may limit the maximum number of levels to which include files can be nested, but the limit shall be at least 15.</P><HR><P><A HREF="ch16.htm">Chapter start</A> <A HREF="ch16.4.htm">Previous page</A> <A HREF="ch16.6.htm">Next page</A></P></BODY></HTML>?? 快捷鍵說明
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