ch16.2.htm
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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> 16.2 `default_nettype</TITLE></HEAD><BODY BGCOLOR="#ffffff"><DIV><HR><P><A HREF="ch16.htm">Chapter start</A> <A HREF="ch16.1.htm">Previous page</A> <A HREF="ch16.3.htm">Next page</A></P></DIV><H1 CLASS="Section"><A NAME="pgfId=170"> </A>16.2 <A NAME="44855"> </A><A NAME="49267"> </A>`<A NAME="marker=42"> </A>default_nettype</H1><P CLASS="Body"><A NAME="pgfId=171"> </A>The directive <B CLASS="Keyword">`default_nettype</B> controls the net type created for <A NAME="marker=43"> </A>implicit net declarations (see <A HREF="/Humuhumu/Files/Prof_Smith/Academic/ASICs/Web/ASICs/HTML/Verilog/LRM/HTML/16/ch03.htm#48381" CLASS="XRef"></A>). It can be used only outside of module definitions. It affects all modules that follow the directive, even across source file boundaries. Multiple <B CLASS="Keyword">`default_nettype</B> directives are allowed. The latest occurence of this directive in the source controls the type of nets that will be implicitly declared. <EM CLASS="-">The following is the syntax of the directive:</EM></P><PRE CLASS="BNFDef"><A NAME="pgfId=172"> </A><B CLASS="Keyword"> `default_nettype</B><A NAME="marker=44"> </A><A NAME="marker=45"> </A><EM CLASS="-"> net_type</EM></PRE><P CLASS="Body"><A NAME="pgfId=175"> </A>The following are the keywords for the net types that can be specified as arguments for the directive:</P><PRE CLASS="BNF"><A NAME="pgfId=185"> </A><B CLASS="codebold"> wire tri tri0</B></PRE><PRE CLASS="BNF"><A NAME="pgfId=186"> </A><B CLASS="codebold"> wand triand tri1</B></PRE><PRE CLASS="BNF"><A NAME="pgfId=187"> </A><B CLASS="codebold"> wor trior trireg</B></PRE><P CLASS="Body"><A NAME="pgfId=188"> </A><EM CLASS="-">When no </EM><B CLASS="Keyword">`default_nettype</B><EM CLASS="-"> directive is present, implicit nets are of type </EM><B CLASS="Keyword">wire</B><EM CLASS="-">.</EM><A NAME="marker=56"> </A><A NAME="marker=73"> </A></P><HR><P><A HREF="ch16.htm">Chapter start</A> <A HREF="ch16.1.htm">Previous page</A> <A HREF="ch16.3.htm">Next page</A></P></BODY></HTML>⌨️ 快捷键说明
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