308 lines
9.1 KiB
HTML
308 lines
9.1 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!--Converted with LaTeX2HTML 2012 (1.2)
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original version by: Nikos Drakos, CBLU, University of Leeds
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* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
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* with significant contributions from:
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Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
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<HTML>
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<HEAD>
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<TITLE>Multiplexor</TITLE>
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<META NAME="description" CONTENT="Multiplexor">
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<td class="navigation" align="left" width="33%"><A HREF="node36.html">Buffer</A></td>
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<td class="navigation" align="center" width="34%"><A HREF="node35.html">Instanciation facilities</A></td>
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<td class="navigation" align="right" width="33%"><A HREF="node38.html">Shifter</A></td>
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<!--End of Navigation Panel-->
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<!--Table of Child-Links-->
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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
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<UL CLASS="ChildLinks">
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<LI><A NAME="tex2html887"
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HREF="node37.html#SECTION00072100000000000000">Name</A>
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<LI><A NAME="tex2html888"
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HREF="node37.html#SECTION00072200000000000000">Synopsys</A>
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<LI><A NAME="tex2html889"
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HREF="node37.html#SECTION00072300000000000000">Description</A>
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<LI><A NAME="tex2html890"
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HREF="node37.html#SECTION00072400000000000000">Parameters</A>
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<LI><A NAME="tex2html891"
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HREF="node37.html#SECTION00072500000000000000">Example</A>
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<LI><A NAME="tex2html892"
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HREF="node37.html#SECTION00072600000000000000">Errors</A>
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<LI><A NAME="tex2html893"
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HREF="node37.html#SECTION00072700000000000000">See Also</A>
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</UL>
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<!--End of Table of Child-Links-->
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<HR>
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<H2><A NAME="SECTION00072000000000000000"></A>
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<A NAME="secmux"></A>
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<BR>
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Multiplexor
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</H2>
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<H3><A NAME="SECTION00072100000000000000">
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Name</A>
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</H3>
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<P>
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Mux - Easy way to instantiate a multiplexor
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<P>
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<H3><A NAME="SECTION00072200000000000000">
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Synopsys</A>
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</H3>
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<P>
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<PRE>
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netOut <= netCmd.Mux ( arg )
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</PRE>
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<P>
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<H3><A NAME="SECTION00072300000000000000">
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Description</A>
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</H3>
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<P>
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This method is a method of net. The net which this method is applied to is the command of the multiplexor. The nets given as parameters are all the input nets. This method returns a net : the output net.
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<BR>
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There are two ways to describe the multiplexor : the argument <code>arg</code> can be a list or a dictionnary.
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<BR>
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Note that it is possible to change the generator instanciated with the <code>SetMux</code> method.
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<P>
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<H3><A NAME="SECTION00072400000000000000">
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Parameters</A>
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</H3>
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<P>
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<UL>
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<LI>List :
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<BR>
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For each value of the command, the corresponding net is specified. All values must be specified.
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<BR>
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For example :
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<PRE>
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out <= cmd.Mux ( [in0, in1, in2, in3] )
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</PRE>
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The net out is then initialised like this :
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<PRE>
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if cmd == 0 : out <= in0
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if cmd == 1 : out <= in1
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if cmd == 2 : out <= in2
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if cmd == 3 : out <= in3
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</PRE>
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</LI>
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<LI>Dictionnary :
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<BR>
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A dictionnary makes the correspondance between a value of the command and the corresponding net.
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<BR>
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For example :
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<PRE>
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out <= cmd.Mux ( {"0" : in0, "1" : in1, "2" : in2, "3" : in3} )
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</PRE>
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This initialisation corresponds to the one before.
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Thanks to the use of a dictionnary, the connections can be clearer :
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<UL>
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<LI><code>'default'</code>: This key of the dictionnary corresponds to all the nets that are not specified
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<BR>
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For example :
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<PRE>
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out <= cmd.Mux ( {"0" : in0, "default" : in1} )
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</PRE>
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This notation corresponds to :
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<PRE>
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if cmd == 0 : out <= in0
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else : out <= in1
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</PRE>
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Note that if there is no <code>'default'</code> key specified and that not all the nets are specified, the non specified nets are set to 0.
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</LI>
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<LI><code>#</code> and <code>?</code> : When a key of the dictionnary begins with <code>#</code>, the number after the <code>#</code> has to be binary and each ? in the number means that this bit is not precised
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<BR>
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For example :
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<PRE>
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out <= cmd.Mux ( {"#01?" : in0, "default" : in1} )
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</PRE>
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This notation corresponds to :
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<PRE>
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if cmd in ( 2, 3 ) : out <= in0
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else : out <= in1
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</PRE>
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</LI>
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<LI><code>,</code> and <code>-</code> : When keys contains thoses symbols, it permits to enumerate intervals
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<BR>
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For example :
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<PRE>
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out <= cmd.Mux ( {"0,4" : in0, "1-3,5" : in1} )
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</PRE>
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This notation corresponds to :
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<PRE>
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if cmd in ( 0, 4 ) : out <= in0
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elif cmd in ( 1, 2, 3, 5) : out <= in1
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else : out <= 0
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</PRE>
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</LI>
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</UL>
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</LI>
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</UL>
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<P>
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<H3><A NAME="SECTION00072500000000000000">
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Example</A>
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</H3>
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<P>
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<PRE>
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class essai ( Model ) :
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def Interface ( self ) :
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self.A = SignalIn ( "a", 4 )
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self.B = SignalIn ( "b", 4 )
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self.C = SignalIn ( "c", 4 )
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self.D = SignalIn ( "d", 4 )
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self.Cmd1 = SignalIn ( "cmd1", 2 )
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self.Cmd2 = SignalIn ( "cmd2", 4 )
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self.S1 = SignalOut ( "s1", 4 )
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self.S2 = SignalOut ( "s2", 4 )
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self.Vdd = VddIn ( "vdd" )
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self.Vss = VssIn ( "vss" )
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def Netlist ( self ) :
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self.S1 <= self.Cmd1.Mux ( [sefl.A, self.B, self.C, self.D] )
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self.S2 <= self.Cmd2.Mux ( { "0" : self.A
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, "1,5-7" : self.B
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, "#1?1?" : self.C
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, "default" : self.D
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} )
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</PRE>
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<P>
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<H3><A NAME="SECTION00072600000000000000">
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Errors</A>
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</H3>
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<P>
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Some errors may occur :
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<UL>
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<LI><code>[Stratus ERROR] Mux : all the nets must have the same lenght.</code>
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<BR>
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All the input nets pust have the same lenght.
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</LI>
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<LI><code>[Stratus ERROR] Mux : there are no input nets.</code>
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<BR>
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The input nets seem to have been forgotten.
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</LI>
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<LI><code>[Stratus ERROR] Mux : wrong argument type.</code>
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<BR>
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The connections of the buses are not described by a list nor a dictionnary.
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</LI>
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<LI><code>[Stratus ERROR] Mux :</code>
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<BR><code>the number of nets does not match with the lenght of the command.</code>
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<BR>
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When using a list, the number of nets has to correspond to the number of possible values of the command.
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</LI>
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<LI><code>[Stratus ERROR] Mux : wrong key.</code>
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<BR>
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One of the key of the dictionnary is not un number, neither a list or an interval.
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</LI>
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<LI><code>[Stratus ERROR] Mux :</code>
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<BR><code>when an interval is specified, the second number of the interval</code>
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<BR><code>must be greater than the first one.</code>
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<BR>
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When creating an interval with "-", the second number has to be greater than the first one.
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</LI>
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<LI><code>[Stratus ERROR] Mux :</code>
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<BR><code>the binary number does not match with the lenght of the command.</code>
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<BR>
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When using the <code>#</code> notation, each digit of the binary number corresponds to a wire of the cmd. The leghts have to correspond.
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</LI>
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<LI><code>[Stratus ERROR] Mux : after #, the number has to be binary.</code>
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<BR>
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When using the <code>#</code> notation, the number has to be binary : one can use 0, 1 or ?.
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</LI>
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</UL>
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<P>
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<H3><A NAME="SECTION00072700000000000000">
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See Also</A>
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</H3>
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<P>
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<A HREF="node3.html#secintroduction"><SPAN CLASS="textit">Introduction</SPAN></A>
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<A HREF="node6.html#secnetlist"><SPAN CLASS="textit">Netlist</SPAN></A>
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<A HREF="node38.html#secshift"><SPAN CLASS="textit">Instanciation of a shifter</SPAN></A>
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<A HREF="node39.html#secreg"><SPAN CLASS="textit">Instanciation of a register</SPAN></A>
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<A HREF="node40.html#secconstant"><SPAN CLASS="textit">Instanciation of constants</SPAN></A>
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<A HREF="node41.html#secbool"><SPAN CLASS="textit">Boolean operations</SPAN></A>
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<A HREF="node42.html#secarithmetic"><SPAN CLASS="textit">Arithmetical operations</SPAN></A>
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<A HREF="node43.html#seccomp"><SPAN CLASS="textit">Comparison operations</SPAN></A>
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<P>
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<DIV CLASS="navigation">
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<hr><table align="center" width="100%" cellpadding="0" cellspacing="2">
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<tr><td class="navigation" align="left" width="33%"><B>Previous</B></td>
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<td class="navigation" align="right" width="33%"><B>Next</B></td>
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</tr><tr>
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<td class="navigation" align="left" width="33%"><A HREF="node36.html">Buffer</A></td>
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<td class="navigation" align="center" width="34%"><A HREF="node35.html">Instanciation facilities</A></td>
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<td class="navigation" align="right" width="33%"><A HREF="node38.html">Shifter</A></td>
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</tr></table>
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<ADDRESS>
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Sophie B<small>ELLOEIL</small><br>20051116.1
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