DpgenShrot

• Name : DpgenShrot - Shift/Rotation Macro-Generator
• Synopsys :

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

• Description : Generates a n bits shift/rotation operator named modelname.
• Terminal Names :
  • op : select the kind of shift/rotation (input, 3 bits)
  • shamt : the shift amount (input, Y bits)
  • i : value to shift (input, n bits)
  • o : output (n bits)
  • 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
• How it works :
  • If the op[0] signal is set to one, performs a right shift/rotation , otherwise left shift/rotation occurs.
  • If the op[1] signal is set to one, performs an arithmetic shift (only meaningful in case of a right shift).
  • If the op[2] signal is set to one, performs a rotation, otherwise performs a shift..
  • shamt specifies the shift amount. The width of this signal (Y) is computed from the operator's width : Y = ceil(log2(n)) - 1
• Example :

  from stratus import *
  
  class inst_shrot ( Model ) :
  
    def Interface ( self ) :
      self.rotop     = SignalIn  (     "rotop", 3 )
      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 ( 'DpgenShrot', 'shrot_4'
               , param = { 'nbit'     : 4
                         , 'physical' : True
                         }
               )
      self.I = Inst ( 'shrot_4', 'inst'
                    , map = { 'op'    : self.rotop
                            , '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) )