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<HTML><HEAD> <META NAME="GENERATOR" CONTENT="Adobe PageMill 2.0 Mac"> <LINK REL="STYLESHEET" HREF="ch04.css"> <TITLE> 4.3 Minimum, typical, maximum delay expressions</TITLE></HEAD><BODY BGCOLOR="#ffffff"><P><A NAME="pgfId=732"></A><HR ALIGN=LEFT></P><P><A HREF="ch04.htm">Chapter start</A> <A HREF="ch04.2.htm">Previous page</A> <A HREF="ch04.4.htm">Next page</A></P><H1>4.3 Minimum, typical, maximum delay expressions</H1><P><P CLASS="Body"><A NAME="pgfId=733"></A>Verilog HDL delay expressionscan be specified as three expressions separated by colons. This triple isintended to represent minimum, typical, and maximum values--in that order.The syntax is as follows:</P><PRE>mintypmax_expression ::= expression | expression <B>:</B> expression <B>:</B> expression</PRE><P><P CLASS="BNFCapBody"><A NAME="pgfId=735"></A>Syntax 4-2: Syntaxfor mintypmax expression</P><P><P CLASS="Body"><A NAME="pgfId=739"></A>Verilog HDL models typicallyspecify three values for delay expressions. The three values allow a designto be tested with minimum, typical, or maximum delay values.</P><P><P CLASS="Body"><A NAME="pgfId=822"></A>Values expressed in min:typ:maxformat can be used in expressions. The min:typ:max format can be used whereverexpressions can appear.</P><P><P CLASS="Body"><A NAME="pgfId=743"></A>1. This example shows an expressionthat defines a single triplet of delay values. The minimum value is thesum of <CODE>a+d</CODE> ; the typical value is <CODE>b+e</CODE> ; the maximumvalue is <CODE>c+f</CODE> , as follows:</P><PRE>(a:b:c) + (d:e:f) </PRE><P><P CLASS="Body"><A NAME="pgfId=745"></A>3. The next example shows sometypical expressions that are used to specify <CODE>min:typ:max</CODE> formatvalues:</P><PRE>val - (32'd 50: 32'd 75: 32'd 100) </PRE><P><HR ALIGN=LEFT></P><P><A HREF="ch04.htm">Chapter start</A> <A HREF="ch04.2.htm">Previous page</A> <A HREF="ch04.4.htm">Next page</A></BODY></HTML>?? 快捷鍵說明
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