TLB/src/AddressEncoder.py

   1 from nmigen import Module, Signal
   2 from nmigen.lib.coding import Encoder, PriorityEncoder
   3
   4 class AddressEncoder():
   5     def __init__(self, width):
   6         # Internal
   7         self.encoder = Encoder(width)
   8         self.p_encoder = PriorityEncoder(width)
   9
  10         # Input
  11         self.i = Signal(width)
  12
  13         # Output
  14         self.single_match = Signal(1)
  15         self.multiple_match = Signal(1)
  16         self.o = Signal(max=width)
  17
  18     def elaborate(self, platform=None):
  19         m = Module()
  20
  21         # Add internal submodules
  22         m.submodules.encoder = self.encoder
  23         m.submodules.p_encoder = self.p_encoder
  24
  25         m.d.comb += [
  26             self.encoder.i.eq(self.i),
  27             self.p_encoder.i.eq(self.i)
  28         ]
  29
  30         # If the priority encoder recieves an input of 0
  31         # If n is 1 then the output is not valid
  32         with m.If(self.p_encoder.n):
  33             m.d.comb += [
  34                 self.single_match.eq(0),
  35                 self.multiple_match.eq(0),
  36                 self.o.eq(0)
  37             ]
  38         # If the priority encoder recieves an input > 0
  39         with m.Else():
  40             # Multiple Match if encoder n is invalid
  41             with m.If(self.encoder.n):
  42                 m.d.comb += [
  43                     self.single_match.eq(0),
  44                     self.multiple_match.eq(1)
  45                 ]
  46             # Single Match if encoder n is valid
  47             with m.Else():
  48                 m.d.comb += [
  49                     self.single_match.eq(1),
  50                     self.multiple_match.eq(0)
  51                 ]
  52             # Always set output based on priority encoder output
  53             m.d.comb += self.o.eq(self.p_encoder.o)
  54         return m