TLB/CAM.py

   1 from nmigen import Array, Module, Signal
   2 from nmigen.lib.coding import Encoder
   3 from nmigen.cli import main
   4
   5 from math import log
   6
   7 from CamEntry import CamEntry
   8
   9 class CAM():
  10     def __init__(self, key_size, data_size, cam_size):
  11         # Internal
  12         entry_array = Array(CamEntry(key_size, data_size) for x in range(cam_size))
  13         encoder_input = Signal(cam_size)
  14
  15         # Input
  16         self.write = Signal(1)
  17         self.key = Signal(key_size)
  18         self.data_in = Signal(key_size)
  19
  20         # Output
  21         self.data_match = Signal(1)
  22         self.data_out = Signal(data_size)
  23
  24         def elaborate(self, platform):
  25             m = Module()
  26
  27             m.d.submodules.encoder = encoder = Encoder(cam_size)
  28
  29             for index in range(cam_size):
  30                 m.d.sync += [
  31                     entry_array[index].write.eq(self.write),
  32                     entry_array[index].key_in.eq(self.key),
  33                     entry_array[index].data_in.eq(self.data_in),
  34                     encoder_input[index].eq(entry_array[index].match)
  35                 ]
  36
  37
  38             m.d.sync += [
  39                 encoder.i.eq(encoder_input),
  40                 #  1. Read request
  41                 #  2. Write request
  42                 If(self.write == 0,
  43                    # 0 denotes a mapping was found
  44                    If(encoder.n == 0,
  45                       self.data_match.eq(0),
  46                       self.data_out.eq(entry_array[encoder.o].data)
  47                     ).Else(
  48                        self.data_match.eq(1)
  49                     )
  50                 ).Else(
  51                     # 0 denotes a mapping was found
  52                     If(encoder.n == 0,
  53                        self.data_match.eq(0),
  54                        entry_array[encoder.o].data_in.eq(self.data_in)
  55                     ).Else(
  56                         # LRU algorithm here
  57                     )
  58                 )
  59
  60             ]
  61
  62             return m
  63