# DpgenNul

- Name : DpgenNul - Zero Detector Macro-Generator
- Synopsys :

      Generate ( 'DpgenNul', modelname
               , param = { 'nbit'     : n
                         , 'physical' : True
                         }
               )

- Description : Generates a `n` bits zero detector named `modelname`.
- Terminal Names :
  - i0 : value to check (input, `n` bits)
  - q : null flag (1 bit)
  - vdd : power
  - vss : ground
- Parameters : Parameters are given in the map `param`.
  - nbit (mandatory) : Defines the size of the generator
  - physical (optional, default value : False) : In order to generate a layout
- Behavior :

      q <= '1' WHEN ( i0 = X"00000000" ) ELSE '0';

- Example :

      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) )