) described in <A HREF="ch07.b.htm#24186" CLASS="XRef">See : Strong X range</A>.</P><P CLASS="Body"><A NAME="pgfId=1598"> </A>The range in <A HREF="ch07.b.htm#24186" CLASS="XRef">See : Strong X range</A> is <B CLASS="Keyword">strong</B> <CODE CLASS="code">x</CODE>, because it is unknown and both of its components' extremes are <B CLASS="Keyword">strong</B>. The extreme of the output of the lower configuration is <B CLASS="Keyword">strong</B> because the lower <B CLASS="Keyword">pmos</B> reduces the strength of the <B CLASS="Keyword">supply0</B> signal. Section <A HREF="ch07.c.htm#75600" CLASS="XRef">See Strength reduction by non-resistive devices</A> discusses this modeling feature.</P><P CLASS="Body"><A NAME="pgfId=1599"> </A><A NAME="98318"> </A></P><DIV><IMG SRC="ch07-24.gif"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1600"> </A>Figure&nbsp;7-15: Strong X range<A NAME="24186"> </A></P><P CLASS="Body"><A NAME="pgfId=1601"> </A>Logic gates produce results with ambiguous strengths as well as tristate drivers. Such a case appears in <A HREF="ch07.b.htm#92076" CLASS="XRef">See : Ambiguous strength from gates</A>. The <B CLASS="Keyword">and</B> gate <CODE CLASS="code">N1</CODE> is declared with <B CLASS="Keyword">highz0</B> strength, and <CODE CLASS="code">N2</CODE> is declared with <B CLASS="Keyword">weak0</B> strength.</P><P CLASS="Body"><A NAME="pgfId=1602"> </A></P><DIV><IMG SRC="ch07-25.gif"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1603"> </A>Figure&nbsp;7-16<A NAME="92076"> </A>: Ambiguous strength from gates</P><P CLASS="Body"><A NAME="pgfId=1604"> </A>In <A HREF="ch07.b.htm#92076" CLASS="XRef">See : Ambiguous strength from gates</A>, register <CODE CLASS="code">b</CODE> has an unspecified<EM CLASS="-"> value, so input to the upper </EM><B CLASS="Keyword">and</B><EM CLASS="-"> gate is </EM><B CLASS="Keyword">strong</B><EM CLASS="-"> </EM><CODE CLASS="code">x</CODE><EM CLASS="-">. The upper </EM><B CLASS="Keyword">and</B><EM CLASS="-"> gate has a strength specification including </EM><B CLASS="Keyword">highz0</B><EM CLASS="-">. The signal from the upper </EM><B CLASS="Keyword">and</B><EM CLASS="-"> gate is a </EM><B CLASS="Keyword">strong</B><EM CLASS="-"> </EM><CODE CLASS="code">H</CODE><EM CLASS="-"> composed of the values as described in <A HREF="ch07.b.htm#78170" CLASS="XRef">See : Ambiguous strength signal from a gate</A>.</EM></P><P CLASS="Body"><A NAME="pgfId=1605"> </A></P><DIV><IMG SRC="ch07-26.gif"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1606"> </A>Figure&nbsp;7-17<A NAME="78170"> </A>: Ambiguous strength signal from a gate</P><P CLASS="Body"><A NAME="pgfId=1607"> </A><CODE CLASS="code">HiZ0</CODE><EM CLASS="-"> is part of the result, because the strength specification for the gate in question specified that strength for an output with a value </EM><CODE CLASS="code">0</CODE><EM CLASS="-">. A strength specification other than high impedance for the </EM><CODE CLASS="code">0</CODE><EM CLASS="-"> value output results in a gate output value </EM><CODE CLASS="code">x</CODE><EM CLASS="-">. The output of the lower </EM><B CLASS="Keyword">and</B><EM CLASS="-"> gate is a </EM><B CLASS="Keyword">weak</B><EM CLASS="-"> </EM><CODE CLASS="code">0</CODE><EM CLASS="-"> as described in <A HREF="ch07.b.htm#31272" CLASS="XRef">See : Weak 0</A>.</EM></P><P CLASS="Body"><A NAME="pgfId=1608"> </A></P><DIV><IMG SRC="ch07-27.gif"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1609"> </A>Figure&nbsp;7-18<A NAME="31272"> </A>: Weak 0</P><P CLASS="Body"><A NAME="pgfId=1610"> </A><EM CLASS="-">When the signals combine, the result is the range (</EM><CODE CLASS="code">36x</CODE><EM CLASS="-">) as described in <A HREF="ch07.b.htm#25868" CLASS="XRef">See : Ambiguous strength in combined gate signals</A>.</EM></P><P CLASS="Body"><A NAME="pgfId=1611"> </A><EM CLASS="-"></EM></P><DIV><IMG SRC="ch07-28.gif"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1612"> </A>Figure&nbsp;7-19<A NAME="25868"> </A>: Ambiguous strength in combined gate signals</P><P CLASS="Body"><A NAME="pgfId=1613"> </A>This figure presents the combination of an ambiguous signal and an unambiguous signal. Such combinations are the topic of the next subsection.</P><P CLASS="SubSection"><A NAME="pgfId=1614"> </A>Ambiguous strength signals and unambiguous signals</P><P CLASS="Body"><A NAME="pgfId=1615"> </A>The combination of a signal with unambiguous strength and known value with another signal of ambiguous strength presents several possible cases. To understand a set of rules governing this type of combination, it is necessary to consider the strength levels of the ambiguous strength signal separately from each other and relative to the unambiguous strength signal. When a signal of known value and unambiguous strength combines with a component of a signal of ambiguous strength, these shall be the effects:</P><OL><P CLASS="NumberedLista"><A NAME="pgfId=1616"> </A>a)	The strength levels of the ambiguous strength signal that are greater than the strength level of the unambiguous signal shall remain in the result.</P><P CLASS="NumberedListb"><A NAME="pgfId=1617"> </A>b)	The strength levels of the ambiguous strength signal that are smaller than or equal to the strength level of the unambiguous signal shall disappear from the result, subject to rule c.</P><P CLASS="NumberedListb"><A NAME="pgfId=1618"> </A>c)	If the operation of rule a and rule b results in a gap in strength levels because the signals are of opposite value, the signals in the gap shall be part of the result.</P></OL><P CLASS="Body"><A NAME="pgfId=1619"> </A>The following figures show some applications of the rules.</P><P CLASS="Body"><A NAME="pgfId=1620"> </A></P><DIV><MAP NAME="ch07-29"></MAP><IMG SRC="ch07-29.gif" USEMAP="#ch07-29"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1621"> </A>Figure&nbsp;7-20<A NAME="56639"> </A>: Elimination of strength levels</P><P CLASS="Body"><A NAME="pgfId=1622"> </A>In <A HREF="ch07.b.htm#56639" CLASS="XRef">See : Elimination of strength levels</A>, the strength levels in the ambiguous strength signal that are smaller than or equal to the strength level of the unambiguous strength signal disappear from the result, demonstrating rule b.</P><P CLASS="Body"><A NAME="pgfId=1623"> </A></P><DIV><MAP NAME="ch07-30"></MAP><IMG SRC="ch07-30.gif" USEMAP="#ch07-30"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1624"> </A>Figure&nbsp;7-21<A NAME="83116"> </A>: Result demonstrating a range and the elimination<BR> of strength levels of two values</P><P CLASS="Body"><A NAME="pgfId=1625"> </A>In <A HREF="ch07.b.htm#83116" CLASS="XRef">See : Result demonstrating a range and the elimination of strength levels of two values</A>, rules a, b, and c apply. The strength levels of the ambiguous strength signal that are of opposite value and lesser strength than the unambiguous strength signal disappear from the result. The strength levels in the ambiguous strength signal that are less than the strength level of the unambiguous strength signal, and of the same value, disappear from the result. The strength level of the unambiguous strength signal and the greater extreme of the ambiguous strength signal define a range in the result.</P><P CLASS="Body"><A NAME="pgfId=1626"> </A></P><DIV><MAP NAME="ch07-31"></MAP><IMG SRC="ch07-31.gif" USEMAP="#ch07-31"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1627"> </A>Figure&nbsp;7-22<A NAME="12338"> </A>: Result demonstrating a range and the elimination<BR> of strength levels of one value</P><P CLASS="Body"><A NAME="pgfId=1628"> </A>In <A HREF="ch07.b.htm#12338" CLASS="XRef">See : Result demonstrating a range and the elimination of strength levels of one value</A>, rules a and b apply. The strength levels in the ambiguous strength signal that are less than the strength level of the unambiguous strength signal disappear from the result. The strength level of the unambiguous strength signal and the strength level at the greater extreme of the ambiguous strength signal define a range in the result.</P><P CLASS="Body"><A NAME="pgfId=1629"> </A></P><DIV><MAP NAME="ch07-32"></MAP><IMG SRC="ch07-32.gif" USEMAP="#ch07-32"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1630"> </A>Figure&nbsp;7-23<A NAME="50715"> </A>: A range of both values</P><P CLASS="Body"><A NAME="pgfId=1631"> </A>In <A HREF="ch07.b.htm#50715" CLASS="XRef">See : A range of both values</A>, rules a, b, and c apply. The greater extreme of the range of strengths for the ambiguous strength signal is larger than the strength level of the unambiguous strength signal. The result is a range defined by the greatest strength in the range of the ambiguous strength signal and by the strength level of the unambiguous strength signal.</P><P CLASS="SubSection"><A NAME="pgfId=1632"> </A><EM CLASS="-"></EM><A NAME="12436"> </A>W<A NAME="marker=523"> </A><A NAME="marker=524"> </A><A NAME="marker=525"> </A>ired logic net types </P><P CLASS="Body"><A NAME="pgfId=1633"> </A><EM CLASS="-">The net types </EM><B CLASS="Keyword">triand</B><EM CLASS="-">, </EM><B CLASS="Keyword">wand</B><EM CLASS="-">, </EM><B CLASS="Keyword">trior</B>, and<EM CLASS="-"> </EM><B CLASS="Keyword">wor</B><A NAME="marker=526"> </A> <EM CLASS="-">shall resolve conflicts when multiple drivers have the same strength. These net types shall resolve signal values by treating signals </EM><A NAME="marker=527"> </A>as<EM CLASS="-"> inputs of logic functions. </EM></P></DIV><DIV><H2 CLASS="Example"><A NAME="pgfId=1634"> </A><EM CLASS="-"></EM></H2><P CLASS="Body"><A NAME="pgfId=1040"> </A><EM CLASS="-">Consider the combination of two signals of unambiguous strength in <A HREF="ch07.b.htm#18033" CLASS="XRef">See : Wired logic with unambiguous strength signals</A>.</EM></P><P CLASS="Body"><A NAME="pgfId=1635"> </A></P><DIV><MAP NAME="ch07-33"></MAP><IMG SRC="ch07-33.gif" USEMAP="#ch07-33"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1636"> </A>Figure&nbsp;7-24<A NAME="18033"> </A>: Wired logic with unambiguous strength signals</P><P CLASS="Body"><A NAME="pgfId=1637"> </A>The combination of the signals in <A HREF="ch07.b.htm#18033" CLASS="XRef">See : Wired logic with unambiguous strength signals</A>, using <I CLASS="Emphasis">wired and</I> logic, produces a result with the same value as the result produced by an <B CLASS="Keyword">and</B> gate with the value of the two signals as its inputs. The combination of signals using <I CLASS="Emphasis">wired or</I> logic produces a result with the same value as the result produced by an <B CLASS="Keyword">or</B> gate with the values of the two signals as its inputs. The strength of the result is the same as the strength of the combined signals in both cases. If the value of the upper signal changes so that both signals in <A HREF="ch07.b.htm#18033" CLASS="XRef">See : Wired logic with unambiguous strength signals</A> possess a value <CODE CLASS="code">1</CODE>, then the results of both types of logic have a value <CODE CLASS="code">1</CODE>.</P><P CLASS="Body"><A NAME="pgfId=1638"> </A>When ambiguous strength signals combine in wired logic, it is necessary to consider the results of all combinations of each of the strength levels in the first signal with each of the strength levels in the second signal, as shown in <A HREF="ch07.b.htm#36385" CLASS="XRef">See : Wired logic and ambiguous strengths</A>.</P><P CLASS="Body"><A NAME="pgfId=1639"> </A></P><DIV><MAP NAME="ch07-34"></MAP><IMG SRC="ch07-34.gif" USEMAP="#ch07-34"></DIV><P CLASS="FigCapBody"><A NAME="pgfId=1640"> </A>Figure&nbsp;7-25<A NAME="36385"> </A>: Wired <A NAME="marker=544"> </A>logic<A NAME="marker=545"> </A> and<A NAME="marker=546"> </A> ambiguous<A NAME="marker=547"> </A><A NAME="marker=548"> </A><A NAME="marker=549"> </A> strengths</P></DIV><HR><P><A HREF="ch07.htm">Chapter&nbsp;&nbsp;start</A>&nbsp;&nbsp;&nbsp;<A HREF="ch07.a.htm">Previous&nbsp;&nbsp;page</A>&nbsp;&nbsp;<A HREF="ch07.c.htm">Next&nbsp;&nbsp;page</A></P></BODY></HTML>