coriolis/stratus1/doc/stratus/man_mux.tex

\subsubsection{Name}

Mux -- Easy way to instantiate a multiplexor

\subsubsection{Synopsys}

\begin{verbatim}
netOut <= netCmd.Mux ( arg )
\end{verbatim}
  
\subsubsection{Description}

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.\\
There are two ways to describe the multiplexor : the argument \verb-arg- can be a list or a dictionnary.\\
\indent Note that it is possible to change the generator instanciated with the \verb-SetMux- method.

\subsubsection{Parameters}

\begin{itemize}
    \item List :\\
    \indent For each value of the command, the corresponding net is specified. All values must be specified.\\
    \indent For example :
    \begin{verbatim}
out <= cmd.Mux ( [in0, in1, in2, in3] )
    \end{verbatim}
    \indent The net out is then initialised like this :
    \begin{verbatim}
if cmd == 0 : out <= in0
if cmd == 1 : out <= in1
if cmd == 2 : out <= in2
if cmd == 3 : out <= in3
    \end{verbatim}
    \item Dictionnary :\\
    \indent A dictionnary makes the correspondance between a value of the command and the corresponding net.\\
    \indent For example :
    \begin{verbatim}
out <= cmd.Mux ( {"0" : in0, "1" : in1, "2" : in2, "3" : in3} )
    \end{verbatim}
    \indent This initialisation corresponds to the one before.
    \indent Thanks to the use of a dictionnary, the connections can be clearer :
    \begin{itemize}
        \item \verb-'default'-: This key of the dictionnary corresponds to all the nets that are not specified\\
        For example :
        \begin{verbatim}
out <= cmd.Mux ( {"0" : in0, "default" : in1} )
        \end{verbatim}
        This notation corresponds to :
        \begin{verbatim}
if cmd == 0 : out <= in0
else        : out <= in1
        \end{verbatim}
        Note that if there is no \verb-'default'- key specified and that not all the nets are specified, the non specified nets are set to 0.
        \item \verb-#- and \verb-?- : When a key of the dictionnary begins with \verb-#-, the number after the \verb-#- has to be binary and each ? in the number means that this bit is not precised\\
        For example :
        \begin{verbatim}
out <= cmd.Mux ( {"#01?" : in0, "default" : in1} )
        \end{verbatim}
        This notation corresponds to :
        \begin{verbatim}
if cmd in ( 2, 3 ) : out <= in0
else               : out <= in1
        \end{verbatim}
        \item \verb-,- and \verb"-" : When keys contains thoses symbols, it permits to enumerate intervals\\
        For example :
        \begin{verbatim}
out <= cmd.Mux ( {"0,4" : in0, "1-3,5" : in1} )
        \end{verbatim}
        This notation corresponds to :
        \begin{verbatim}
if   cmd in ( 0, 4 )      : out <= in0
elif cmd in ( 1, 2, 3, 5) : out <= in1
else                      : out <= 0
        \end{verbatim}
    \end{itemize}
\end{itemize}
          
\subsubsection{Example}

\begin{verbatim}
class essai ( Model ) :

  def Interface ( self ) :
    self.A    = SignalIn  (    "a", 4 )
    self.B    = SignalIn  (    "b", 4 )
    self.C    = SignalIn  (    "c", 4 )
    self.D    = SignalIn  (    "d", 4 )
    
    self.Cmd1 = SignalIn  ( "cmd1", 2 )
    self.Cmd2 = SignalIn  ( "cmd2", 4 )
    
    self.S1   = SignalOut (   "s1", 4 )
    self.S2   = SignalOut (   "s2", 4 )

    self.Vdd = VddIn  ( "vdd" )
    self.Vss = VssIn  ( "vss" )
	
  def Netlist ( self ) :

    self.S1 <= self.Cmd1.Mux ( [sefl.A, self.B, self.C, self.D] ) 

    self.S2 <= self.Cmd2.Mux ( { "0"       : self.A
                               , "1,5-7"   : self.B
                               , "#1?1?"   : self.C
                               , "default" : self.D
                             } )
\end{verbatim}
    
\subsubsection{Errors}
    
Some errors may occur :
\begin{itemize}
    \item \verb-[Stratus ERROR] Mux : all the nets must have the same lenght.-\\All the input nets pust have the same lenght.
    \item \verb-[Stratus ERROR] Mux : there are no input nets.-\\The input nets seem to have been forgotten.
    \item \verb-[Stratus ERROR] Mux : wrong argument type.-\\The connections of the buses are not described by a list nor a dictionnary.
    \item \verb-[Stratus ERROR] Mux :-\\\verb-the number of nets does not match with the lenght of the command.-\\When using a list, the number of nets has to correspond to the number of possible values of the command.
    \item \verb-[Stratus ERROR] Mux : wrong key.-\\One of the key of the dictionnary is not un number, neither a list or an interval.
    \item \verb-[Stratus ERROR] Mux :-\\\verb-when an interval is specified, the second number of the interval-\\\verb-must be greater than the first one.-\\When creating an interval with "-", the second number has to be greater than the first one.
    \item \verb-[Stratus ERROR] Mux :-\\\verb-the binary number does not match with the lenght of the command.-\\When using the \verb-#- notation, each digit of the binary number corresponds to a wire of the cmd. The leghts have to correspond.
    \item \verb-[Stratus ERROR] Mux : after #, the number has to be binary.-\\When using the \verb-#- notation, the number has to be binary : one can use 0, 1 or ?.
\end{itemize}

\begin{htmlonly}

\subsubsection{See Also}

\hyperref[ref]{\emph{Introduction}}{}{Introduction}{secintroduction}
\hyperref[ref]{\emph{Netlist}}{}{Netlist}{secnetlist}
\hyperref[ref]{\emph{Instanciation of a shifter}}{}{Shifter}{secshift}
\hyperref[ref]{\emph{Instanciation of a register}}{}{Reg}{secreg}
\hyperref[ref]{\emph{Instanciation of constants}}{}{Constant}{secconstant}
\hyperref[ref]{\emph{Boolean operations}}{}{Boolean}{secbool}
\hyperref[ref]{\emph{Arithmetical operations}}{}{Arithmetic}{secarithmetic}
\hyperref[ref]{\emph{Comparison operations}}{}{Comparison}{seccomp}

\end{htmlonly}