\begin{itemize}
    \item \textbf{Name} : DpgenShift -- Shifter Macro-Generator
    \item \textbf{Synopsys} :
\begin{verbatim}
Generate ( 'DpgenShift', modelname
         , param = { 'nbit'     : n
                   , 'physical' : True         
                   }
         )
\end{verbatim}
    \item \textbf{Description} : Generates a \verb-n- bits shifter named \verb-modelname-.
    \item \textbf{Terminal Names} :
    \begin{itemize}
        \item \textbf{op} : select the kind of shift (input, 2 bits)
        \item \textbf{shamt} : the shift amount (input, \verb-Y- bits)
        \item \textbf{i} : value to shift (input, \verb-n- bits)
        \item \textbf{o} : output (\verb-n- bits)
        \item \textbf{vdd} : power
        \item \textbf{vss} : ground
    \end{itemize}
    \item \textbf{Parameters} : Parameters are given in the map \verb-param-.
    \begin{itemize}
        \item \textbf{nbit} (mandatory) : Defines the size of the generator
        \item \textbf{physical} (optional, default value : False) : In order to generate a layout
    \end{itemize}
    \item \textbf{How it works} :
    \begin{itemize}
        \item If the \verb-op[0]- signal is set to \verb-one-, performs a right shift, performs a left shift otherwise.
        \item If the \verb-op[1]- signal is set to \verb-one-, performs an arithmetic shift (only meaningful in case of a right shift).
        \item shamt : specifies the shift amount. The width of this signal (\verb-Y-) is computed from the operator's width : \verb-Y = ceil(log2(n)) -- 1
    \end{itemize}    
%    \item \textbf{Behavior} :
%\begin{verbatim}
%\end{verbatim}
    \item \textbf{Example} :
\begin{verbatim}
from stratus import *

class inst_shifter ( Model ) :

  def Interface ( self ) :
    self.instop    = SignalIn  (    "instop", 2 )
    self.instshamt = SignalIn  ( "instshamt", 2 )
    self.insti     = SignalIn  (     "insti", 4 )
    self.insto     = SignalOut (     "insto", 4 )
    
    self.vdd = VddIn ( "vdd" )
    self.vss = VssIn ( "vss" )
    
  def Netlist ( self ) :
    Generate ( 'DpgenShifter', 'shifter_4'
             , param = { 'nbit'     : 4
                       , 'physical' : True
                       }
             )
    self.I = Inst ( 'shifter_4', 'inst'
                  , map = { 'op'    : self.instop
                          , 'shamt' : self.instshamt
                          , 'i'     : self.insti
                          , 'o'     : self.insto
                          , 'vdd'   : self.vdd
                          , 'vss'   : self.vss
                          }
                  )
    
  def Layout ( self ) :
    Place ( self.I, NOSYM, Ref(0, 0) )
\end{verbatim}
\end{itemize}
