?? ch14.3.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="ch14.css"><TITLE> 14.3 Timescale system tasks</TITLE></HEAD><BODY BGCOLOR="#ffffff"><DIV><HR><P><A HREF="ch14.htm">Chapter start</A> <A HREF="ch14.2.htm">Previous page</A> <A HREF="ch14.4.htm">Next page</A></P></DIV><H1 CLASS="Section"><A NAME="pgfId=987"> </A>14.3 <A NAME="88165"> </A>Timescale system tasks</H1><P CLASS="Body"><A NAME="pgfId=989"> </A>The following system tasks display and set timescale information: </P><OL><P CLASS="NumberedLista"><A NAME="pgfId=990"> </A>a) <B CLASS="Keyword">$printtimescale </B></P><P CLASS="NumberedListb"><A NAME="pgfId=991"> </A>b) <B CLASS="Keyword">$timeformat</B></P></OL><P CLASS="SubSection"><A NAME="pgfId=992"> </A><A NAME="marker=219"> </A><A NAME="marker=220"> </A>$printtimescale</P><P CLASS="Body"><A NAME="pgfId=994"> </A>The<B CLASS="boldemphasis"> </B><B CLASS="Keyword">$printtimescale</B> system task displays the time unit and precision for a particular module.</P><DIV><H2 CLASS="Syntax"><A NAME="pgfId=995"> </A></H2><PRE CLASS="BNFDef"><A NAME="pgfId=996"> </A> <B CLASS="Keyword">$printtimescale</B> [ <B CLASS="Keyword">(</B> hierarchical_name<B CLASS="Keyword"> )</B> ] <B CLASS="Keyword">;</B></PRE><P CLASS="Body"><A NAME="pgfId=1241"> </A>This system task can be specified with or without an argument.</P><UL><LI CLASS="DashedList"><A NAME="pgfId=998"> </A>When no argument is specified, <B CLASS="Keyword">$printtimescale</B> displays the time unit and precision of the module that is the current scope.</LI><LI CLASS="DashedList"><A NAME="pgfId=999"> </A>When an argument is specified, <B CLASS="Keyword">$printtimescale</B><CODE CLASS="code"> </CODE>displays the time unit and precision of the module passed to it.</LI></UL><P CLASS="Body"><A NAME="pgfId=1000"> </A>The timescale information appears in the following format:</P><PRE CLASS="CodeIndent"><A NAME="pgfId=1001"> </A>Time scale of (module_name) is unit / precision</PRE></DIV><DIV><H2 CLASS="Example"><A NAME="pgfId=1002"> </A></H2><P CLASS="Body"><A NAME="pgfId=1003"> </A></P><DIV><IMG SRC="ch14-15.gif"></DIV><P CLASS="Body"><A NAME="pgfId=1005"> </A>In this example, module <CODE CLASS="code">a_dat</CODE> invokes the <B CLASS="Keyword">$printtimescale</B> system task to display timescale information about another module <CODE CLASS="code">c_dat</CODE>, which is instantiated in module <CODE CLASS="code">b_dat</CODE>.</P><P CLASS="Body"><A NAME="pgfId=1006"> </A>The information about<CODE CLASS="code"> c_dat</CODE> is displayed in the following format:</P><PRE CLASS="CodeIndent"><A NAME="pgfId=1007"> </A>Time scale of (b_dat.c1) is 1ns / 1ns<A NAME="marker=222"> </A><A NAME="marker=223"> </A></PRE><P CLASS="SubSection"><A NAME="pgfId=1008"> </A><A NAME="73834"> </A><A NAME="marker=224"> </A><A NAME="marker=225"> </A><A NAME="marker=226"> </A>$timeformat</P></DIV><DIV><H2 CLASS="Syntax"><A NAME="pgfId=1013"> </A></H2><PRE CLASS="BNFDef"><A NAME="pgfId=1014"> </A><B CLASS="Keyword"> $timeformat</B> [ <B CLASS="Keyword">(</B> units_number <B CLASS="Keyword">,</B> precision_number <B CLASS="Keyword">,</B> suffix_string <B CLASS="Keyword">,</B> minimum_field_width <B CLASS="Keyword">)</B> ] <B CLASS="Keyword">;</B></PRE><P CLASS="Body"><A NAME="pgfId=1010"> </A>The<B CLASS="boldemphasis"> </B><B CLASS="Keyword">$timeformat</B> system task performs the following two functions:</P><UL><LI CLASS="DashedList"><A NAME="pgfId=1011"> </A>It specifies how the <CODE CLASS="code">%t</CODE> format specification reports time information for the <B CLASS="Keyword">$write</B>,<CODE CLASS="code"> </CODE><B CLASS="Keyword">$display</B>,<CODE CLASS="code"> </CODE><B CLASS="Keyword">$strobe</B>,<CODE CLASS="code"> </CODE><B CLASS="Keyword">$monitor</B>,<CODE CLASS="code"> </CODE><B CLASS="Keyword">$fwrite</B>,<CODE CLASS="code"> </CODE><B CLASS="Keyword">$fdisplay</B>,<CODE CLASS="code"> </CODE><B CLASS="Keyword">$fstrobe</B>,<CODE CLASS="code"> </CODE>and <B CLASS="Keyword">$fmonitor</B> group of system tasks.</LI><LI CLASS="DashedList"><A NAME="pgfId=1012"> </A>It specifies the time unit for delays entered interactively.</LI></UL><P CLASS="Body"><A NAME="pgfId=1291"> </A>The units number argument must be an integer in the range from 0 to 15. This argument represents the time unit as follows:</P><TABLE><CAPTION><P CLASS="TableTitle"><A NAME="pgfId=800"> </A>Table 14-7<CODE CLASS="code">: </CODE><B CLASS="Keyword">$timeformat</B> units_number arguments</P></CAPTION><TR><TH ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=937"> </A>Unit Number</P></TH><TH ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=940"> </A>Time Unit</P></TH><TH ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=950"> </A>Unit Number</P></TH><TH ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=953"> </A>Time Unit</P></TH></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=960"> </A>0</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=962"> </A>1 s</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=968"> </A>-8</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=977"> </A>10 ns</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=984"> </A>-1</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=988"> </A>100 ms</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=993"> </A>-9</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1009"> </A>1 ns</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1323"> </A>-2</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1324"> </A>10 ms</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1325"> </A>-10</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1326"> </A>100 ps</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1327"> </A>-3</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1328"> </A>1 ms</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1329"> </A>-11</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1332"> </A>10 ps</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1333"> </A>-4</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1334"> </A>100 us</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1335"> </A>-12</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1336"> </A>1 ps</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1337"> </A>-5</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1338"> </A>10 us</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1354"> </A>-13</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1356"> </A>100 fs</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1357"> </A>-6</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1358"> </A>1 us</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1359"> </A>-14</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1360"> </A>10 fs</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1361"> </A>-7</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1362"> </A>100 ns</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1363"> </A>-15</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1364"> </A>1 fs</P></TD></TR></TABLE><P CLASS="Body"><A NAME="pgfId=1018"> </A>The<B CLASS="boldemphasis"> </B><B CLASS="Keyword">$timeformat</B><CODE CLASS="code"> s</CODE>ystem task performs the following two operations:</P><UL><LI CLASS="DashedList"><A NAME="pgfId=1019"> </A>It sets the time unit for all later entered delays entered interactively. </LI><LI CLASS="DashedList"><A NAME="pgfId=1020"> </A>It sets the time unit, precision number, suffix string, and minimum field width for all <CODE CLASS="code">%t f</CODE>ormats specified in all modules that follow in the source description until another <B CLASS="Keyword">$timeformat</B> <CODE CLASS="code">s</CODE>ystem task is invoked.</LI></UL><P CLASS="Body"><A NAME="pgfId=1021"> </A>The default <B CLASS="Keyword">$timeformat</B><CODE CLASS="code"> s</CODE>ystem task arguments are as follows:</P><TABLE BORDER="1"><CAPTION><P CLASS="TableTitle"><A NAME="pgfId=773"> </A>Table 14-8<CODE CLASS="code">: </CODE><B CLASS="Keyword">$timeformat </B>default value for arguments</P></CAPTION><TR><TH ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=1017"> </A>Argument</P></TH><TH ROWSPAN="1" COLSPAN="1"><P CLASS="CellHeading"><A NAME="pgfId=1365"> </A>Default</P></TH></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1366"> </A><CODE CLASS="code">units_number</CODE></P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1371"> </A>the smallest time precision argument of all the <B CLASS="Keyword">`timescale</B> compiler directives in the source description</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1368"> </A>precision_number</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1369"> </A>0</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1370"> </A>suffix_string</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1374"> </A>a null character string</P></TD></TR><TR><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1372"> </A>minimum_field_width</P></TD><TD ROWSPAN="1" COLSPAN="1"><P CLASS="CellBody"><A NAME="pgfId=1373"> </A>20</P></TD></TR></TABLE></DIV><DIV><H2 CLASS="Example"><A NAME="pgfId=1024"> </A></H2><P CLASS="Body"><A NAME="pgfId=1292"> </A>The following example shows the use of <CODE CLASS="code">%t</CODE> with the <B CLASS="Keyword">$timeformat</B><CODE CLASS="code"> s</CODE>ystem task to specify a uniform time unit, time precision, and format for timing information.</P><P CLASS="Body"><A NAME="pgfId=1025"> </A></P><DIV><IMG SRC="ch14-16.gif"></DIV><P CLASS="Body"><A NAME="pgfId=1027"> </A>The contents of file <CODE CLASS="code">a1.dat</CODE> is as follows:</P><PRE CLASS="CodeIndent"><A NAME="pgfId=1028"> </A>a1_dat: 0.00000 ns in1= x o1=xa1_dat: 10.00000 ns in1= 0 o1=xa1_dat: 20.00000 ns in1= 1 o1=0a1_dat: 30.00000 ns in1= 1 o1=1</PRE><P CLASS="Body"><A NAME="pgfId=1033"> </A>The contents of file <CODE CLASS="code">a2.dat </CODE>are as follows:</P><PRE CLASS="CodeIndent"><A NAME="pgfId=1029"> </A>a2_dat: 0.00000 ns in2=x o2=xa2_dat: 10.00000 ns in2=0 o2=xa2_dat: 20.00000 ns in2=1 o2=0a2_dat: 30.00000 ns in2=1 o2=1</PRE><P CLASS="Body"><A NAME="pgfId=1030"> </A>In this example, the times of events written to the files by the <B CLASS="Keyword">$fmonitor</B><CODE CLASS="code"> </CODE>system task in modules<CODE CLASS="code"> a1_dat</CODE> and <CODE CLASS="code">a2_dat</CODE> are reported as multiples of 1 nanosecond--even though the time units for these modules are 1 femtosecond and 1 picosecond respectively--because the first argument of the <B CLASS="Keyword">$timeformat</B> system task is <CODE CLASS="code">-9 </CODE>and<CODE CLASS="code"> </CODE>the <CODE CLASS="code">%t </CODE>format specification is included in the arguments to <B CLASS="Keyword">$fmonitor</B><CODE CLASS="code">.</CODE> This time information is reported after the module names with five fractional digits, followed by an<CODE CLASS="code"> </CODE>"<CODE CLASS="code">ns</CODE>" character string in a space wide enough for 10 ASCII characters<A NAME="marker=232"> </A>.<A NAME="marker=233"> </A></P></DIV><HR><P><A HREF="ch14.htm">Chapter start</A> <A HREF="ch14.2.htm">Previous page</A> <A HREF="ch14.4.htm">Next page</A></P></BODY></HTML>?? 快捷鍵說明
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