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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="ch13.css"><TITLE> 13.5 Mixing module path delays and distributed delays</TITLE></HEAD><BODY BGCOLOR="#ffffff"><DIV><HR><P><A HREF="ch13.htm">Chapter start</A> <A HREF="ch13.4.htm">Previous page</A> <A HREF="ch13.6.htm">Next page</A></P></DIV><H1 CLASS="Section"><A NAME="pgfId=307"> </A>13.5 <A NAME="marker=61"> </A>Mixing module path delays and distributed delays</H1><P CLASS="Body"><A NAME="pgfId=313"> </A>If a module contains module path delays and distributed delays (delays on primitive instances within the module), the larger of the two delays for each path shall be used.</P><DIV><H3 CLASS="Example"><A NAME="pgfId=325"> </A></H3><P CLASS="Body"><A NAME="pgfId=326"> </A><A HREF="ch13.5.htm#internal delays" CLASS="XRef">See : Module path delays longer than distributed delays</A> illustrates a simple circuit modeled with a combination of distributed delays and path delays (only the D input to Q output path is illustrated). Here, the delay on the module path from input <CODE CLASS="code">D</CODE> to output <CODE CLASS="code">Q</CODE> = <CODE CLASS="code">22</CODE>, while the sum of the distributed delays = <CODE CLASS="code">0</CODE> + <CODE CLASS="code">1</CODE> = <CODE CLASS="code">1</CODE>. Therefore, a transition on <CODE CLASS="code">Q</CODE> caused by a transition on <CODE CLASS="code">D</CODE> will occur <CODE CLASS="code">22</CODE> time units after the transition on <CODE CLASS="code">D</CODE>. </P><P CLASS="Body"><A NAME="pgfId=396"> </A></P><DIV><IMG SRC="ch13-25.gif"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=397"> </A>Figure 13-3<A NAME="internal delays"> </A>: Module path delays longer than distributed delays</P><P CLASS="Body"><A NAME="pgfId=291"> </A><BR>In <A HREF="ch13.5.htm#16881" CLASS="XRef">See : Module path delays shorter than distributed delays</A> below, the delay on the module path from <CODE CLASS="code">D</CODE> to <CODE CLASS="code">Q</CODE> = <CODE CLASS="code">22</CODE>, but the distributed delays along that module path now add up to <CODE CLASS="code">10</CODE> + <CODE CLASS="code">20</CODE> = <CODE CLASS="code">30</CODE>. Therefore, an event on <CODE CLASS="code">Q</CODE> caused by an event on <CODE CLASS="code">D</CODE> will occur <CODE CLASS="code">30</CODE> time units after the event on <CODE CLASS="code">D</CODE>.<A NAME="marker=105"> </A></P><P CLASS="Body"><A NAME="pgfId=445"> </A></P><DIV><IMG SRC="ch13-26.gif"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=460"> </A>Figure 13-4<A NAME="16881"> </A>: Module path delays shorter than distributed delays</P></DIV><HR><P><A HREF="ch13.htm">Chapter start</A> <A HREF="ch13.4.htm">Previous page</A> <A HREF="ch13.6.htm">Next page</A></P></BODY></HTML>?? 快捷鍵說(shuō)明
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