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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="ch07.css"><TITLE> 7.1 Gate and switch declaration syntax </TITLE></HEAD><BODY BGCOLOR="#ffffff"><DIV><HR><P><A HREF="ch07.htm">Chapter start</A> <A HREF="ch07.htm">Previous page</A> <A HREF="ch07.2.htm">Next page</A></P></DIV><H1 CLASS="Section"><A NAME="pgfId=1189"> </A>7.1 <A NAME="93218"> </A>Gate and switch declaration syntax </H1><P CLASS="Body"><A NAME="pgfId=1407"> </A><A HREF="ch07.1.htm#42180" CLASS="XRef">See : Syntax for gate instantiation</A> shows the gate and switch declaration <A NAME="marker=117"> </A><A NAME="marker=118"> </A><A NAME="marker=119"> </A><A NAME="marker=120"> </A>syntax.</P><P CLASS="Body"><A NAME="pgfId=1408"> </A>A gate or a switch instance declaration shall have the following specifications:</P><UL><LI CLASS="DashedList"><A NAME="pgfId=1163"> </A>the keyword that names the type of gate or switch primitive </LI><LI CLASS="DashedList"><A NAME="pgfId=1409"> </A>an optional <I CLASS="Emphasis">drive strength</I> </LI><LI CLASS="DashedList"><A NAME="pgfId=1359"> </A>an optional <I CLASS="Emphasis">propagation delay</I> </LI><LI CLASS="DashedList"><A NAME="pgfId=1360"> </A>an optional identifier that names each gate or switch instance</LI><LI CLASS="DashedList"><A NAME="pgfId=645"> </A>an optional range for <I CLASS="Emphasis">array of instances</I></LI><LI CLASS="DashedList"><A NAME="pgfId=1164"> </A>the terminal connection list</LI></UL><P CLASS="Body"><A NAME="pgfId=1361"> </A>Multiple instances of the one type of gate or switch primitive can be declared as a comma separated list. All such instances shall have the same drive strength and the delay specification.</P><P CLASS="Body"><A NAME="pgfId=1404"> </A></P><DIV><IMG SRC="ch07-1.gif"></DIV><P CLASS="BNFCapBody"><A NAME="pgfId=1412"> </A>Syntax 7-1<A NAME="42180"> </A>: Syntax for gate instantiation</P><P CLASS="SubSection"><A NAME="pgfId=1413"> </A>The gate type<A NAME="marker=123"> </A> specification</P><P CLASS="Body"><A NAME="pgfId=1414"> </A>A gate or switch instance declaration shall begin with the keyword that specifies the gate or switch primitive being used by the instances that follow in the declaration. <A HREF="ch07.1.htm#85869" CLASS="XRef">See : Built-in gates and switches</A> lists the keywords that shall begin a gate or a switch instance declaration.</P><TABLE><CAPTION><P CLASS="TableTitle"><A NAME="pgfId=1702"> </A>Table 7-1<A NAME="85869"> </A>: Built-in gates and switches</P></CAPTION><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=1165"> </A>n_input gates</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=670"> </A>n_output gates</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=1174"> </A>tristate gates</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=1192"> </A>pull gates</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=1194"> </A>MOS switches</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=1694"> </A>bidirectional switches</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1140"> </A>and</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1701"> </A>buf</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1459"> </A>bufif0</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1142"> </A>pulldown</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1143"> </A>cmos</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1166"> </A>rtran</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1144"> </A>nand</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1460"> </A>not</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1141"> </A>bufif1 </P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1167"> </A>pullup</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1422"> </A>nmos</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1689"> </A>rtranif0</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1138"> </A>nor</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1696"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1148"> </A>notif0</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1146"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1147"> </A>pmos</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1168"> </A>rtranif1</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1149"> </A>or</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1698"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1145"> </A>notif1</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1151"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1152"> </A>rcmos</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1169"> </A>tran</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1153"> </A>xnor</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1699"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1154"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1155"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1156"> </A>rnmos</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1170"> </A>tranif0</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1157"> </A>xor</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1700"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1158"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1159"> </A></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1160"> </A>rpmos</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1171"> </A>tranif1</P></TD></TR></TABLE><P CLASS="Body"><A NAME="pgfId=1415"> </A>Explanation of the built-in gates and switches shown in <A HREF="ch07.1.htm#85869" CLASS="XRef">See : Built-in gates and switches</A> begin in <A HREF="ch07.2.htm#56809" CLASS="XRef">See And, nand, nor, or, xor, and xnor gates</A>.</P><P CLASS="SubSection"><A NAME="pgfId=1416"> </A>The drive strength<A NAME="marker=134"> </A> specification</P><P CLASS="Body"><A NAME="pgfId=1417"> </A>An optional drive strength specification shall specify the <I CLASS="Emphasis">strength</I><A NAME="marker=135"> </A> of the logic values on the output terminals of the gate instance. Only the instances of the gate primitives shown in<A NAME="marker=136"> </A> <A HREF="ch07.1.htm#70462" CLASS="XRef">See : Valid gate types for strength specifications</A> can have the drive strength specification. </P><TABLE><CAPTION><P CLASS="TableTitle"><A NAME="pgfId=1178"> </A>Table 7-2<A NAME="70462"> </A>: Valid gate types for strength specifications</P>?? 快捷鍵說明
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