\begin{itemize}
    \item \textbf{Name} : DpgenNul -- Zero Detector Macro-Generator
    \item \textbf{Synopsys} :
\begin{verbatim}
Generate ( 'DpgenNul', modelname
         , param = { 'nbit'     : n
                   , 'physical' : True         
                   }
         )
\end{verbatim}
    \item \textbf{Description} : Generates a \verb-n- bits zero detector named \verb-modelname-.
    \item \textbf{Terminal Names} :
    \begin{itemize}
        \item \textbf{i0} : value to check (input, \verb-n- bits)
        \item \textbf{q} : null flag (1 bit)
        \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{Behavior} :
\begin{verbatim}
q <= '1' WHEN ( i0 = X"00000000" ) ELSE '0';
\end{verbatim}
    \item \textbf{Example} :
\begin{verbatim}
from stratus import *

class inst_nul ( Model ) :

  def Interface ( self ) :
    self.i = SignalIn  ( "i", 4 )
    self.o = SignalOut ( "o", 1 )
    
    self.vdd = VddIn ( "vdd" )
    self.vss = VssIn ( "vss" )
    
  def Netlist ( self ) :
    Generate ( 'DpgenNul', 'nul_4'
             , param = { 'nbit'     : 4
                       , 'physical' : True
                       }
             )
    self.I = Inst ( 'nul_4', 'inst'
                   , map = { 'i0'  : self.i
                           , 'nul' : self.o
                           , 'vdd' : self.vdd
                           , 'vss' : self.vss
                           }
                   )
      
  def Layout ( self ) :
    Place ( self.I, NOSYM, Ref(0, 0) )
\end{verbatim}
\end{itemize}
