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<HTML><HEAD> <META NAME="GENERATOR" CONTENT="Adobe PageMill 2.0 Mac"> <LINK REL="STYLESHEET" HREF="ch03.css"> <TITLE> 3.4 Strengths</TITLE></HEAD><BODY BGCOLOR="#ffffff"><P><A NAME="pgfId=452"></A><HR ALIGN=LEFT></P><P><A HREF="ch03.htm">Chapter start</A> <A HREF="ch03.3.htm">Previous page</A> <A HREF="ch03.5.htm">Next page</A></P><H1>3.4 Strengths</H1><P><P CLASS="Body"><A NAME="pgfId=454"></A>There are two types of <I>strengths</I>that can be specified in a net declaration. They are as follows:</P><P><P CLASS="Type"><A NAME="pgfId=378"></A><I>charge strength</I> shallbe used when declaring a net of type <B>trireg</B></P><P><P CLASS="Type"><A NAME="pgfId=384"></A><I>drive strength</I> shallbe used when placing a continuous assignment on a net in the same statementthat declares the net</P><P><P CLASS="Body"><A NAME="pgfId=457"></A>Gate declarations can also specifya drive strength. See Section 7 for more information on gates and for informationon strengths.</P><P><P CLASS="SubSection"><A NAME="pgfId=546"></A>Charge strength</P><P><P CLASS="Body"><A NAME="pgfId=460"></A>The charge strength specificationshall be used only with trireg nets. A trireg net shall be used to modelcharge storage; charge strength shall specify the relative size of the capacitanceindicated by one of the following keywords:</P><UL> <LI><A NAME="pgfId=461"></A><B>small</B> <LI><A NAME="pgfId=462"></A><B>medium</B> <LI><A NAME="pgfId=463"></A><B>large</B></UL><P><P CLASS="Body"><A NAME="pgfId=464"></A>The default charge strength ofa trireg net shall be <B>medium</B>.</P><P><P CLASS="Body"><A NAME="pgfId=418"></A>A trireg<CODE> </CODE>net canmodel a charge storage node whose charge decays over time. The simulationtime of a charge decay shall be specified in the delay specification forthe trireg net (see 7.15.2).</P><P><P CLASS="SubSection"><A NAME="pgfId=450"></A>Drive strength</P><P><P CLASS="Body"><A NAME="pgfId=421"></A>The drive strength specificationallows a continuous assignment to be placed on a net in the same statementthat declares that net. See Section 6 for more details. Net strength propertiesare described in detail in Section 7.</P><P><HR ALIGN=LEFT></P><P><A HREF="ch03.htm">Chapter start</A> <A HREF="ch03.3.htm">Previous page</A> <A HREF="ch03.5.htm">Next page</A></BODY></HTML>?? 快捷鍵說明
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