nmigen/test/test_lib_coding.py

   1 from .utils import *
   2 from ..hdl import *
   3 from ..asserts import *
   4 from ..back.pysim import *
   5 from ..lib.coding import *
   6
   7
   8 class EncoderTestCase(FHDLTestCase):
   9     def test_basic(self):
  10         enc = Encoder(4)
  11         def process():
  12             self.assertEqual((yield enc.n), 1)
  13             self.assertEqual((yield enc.o), 0)
  14
  15             yield enc.i.eq(0b0001)
  16             yield Settle()
  17             self.assertEqual((yield enc.n), 0)
  18             self.assertEqual((yield enc.o), 0)
  19
  20             yield enc.i.eq(0b0100)
  21             yield Settle()
  22             self.assertEqual((yield enc.n), 0)
  23             self.assertEqual((yield enc.o), 2)
  24
  25             yield enc.i.eq(0b0110)
  26             yield Settle()
  27             self.assertEqual((yield enc.n), 1)
  28             self.assertEqual((yield enc.o), 0)
  29
  30         sim = Simulator(enc)
  31         sim.add_process(process)
  32         sim.run()
  33
  34
  35 class PriorityEncoderTestCase(FHDLTestCase):
  36     def test_basic(self):
  37         enc = PriorityEncoder(4)
  38         def process():
  39             self.assertEqual((yield enc.n), 1)
  40             self.assertEqual((yield enc.o), 0)
  41
  42             yield enc.i.eq(0b0001)
  43             yield Settle()
  44             self.assertEqual((yield enc.n), 0)
  45             self.assertEqual((yield enc.o), 0)
  46
  47             yield enc.i.eq(0b0100)
  48             yield Settle()
  49             self.assertEqual((yield enc.n), 0)
  50             self.assertEqual((yield enc.o), 2)
  51
  52             yield enc.i.eq(0b0110)
  53             yield Settle()
  54             self.assertEqual((yield enc.n), 0)
  55             self.assertEqual((yield enc.o), 1)
  56
  57         sim = Simulator(enc)
  58         sim.add_process(process)
  59         sim.run()
  60
  61
  62 class DecoderTestCase(FHDLTestCase):
  63     def test_basic(self):
  64         dec = Decoder(4)
  65         def process():
  66             self.assertEqual((yield dec.o), 0b0001)
  67
  68             yield dec.i.eq(1)
  69             yield Settle()
  70             self.assertEqual((yield dec.o), 0b0010)
  71
  72             yield dec.i.eq(3)
  73             yield Settle()
  74             self.assertEqual((yield dec.o), 0b1000)
  75
  76             yield dec.n.eq(1)
  77             yield Settle()
  78             self.assertEqual((yield dec.o), 0b0000)
  79
  80         sim = Simulator(dec)
  81         sim.add_process(process)
  82         sim.run()
  83
  84
  85 class ReversibleSpec(Elaboratable):
  86     def __init__(self, encoder_cls, decoder_cls, args):
  87         self.encoder_cls = encoder_cls
  88         self.decoder_cls = decoder_cls
  89         self.coder_args  = args
  90
  91     def elaborate(self, platform):
  92         m = Module()
  93         enc, dec = self.encoder_cls(*self.coder_args), self.decoder_cls(*self.coder_args)
  94         m.submodules += enc, dec
  95         m.d.comb += [
  96             dec.i.eq(enc.o),
  97             Assert(enc.i == dec.o)
  98         ]
  99         return m
 100
 101
 102 class HammingDistanceSpec(Elaboratable):
 103     def __init__(self, distance, encoder_cls, args):
 104         self.distance    = distance
 105         self.encoder_cls = encoder_cls
 106         self.coder_args  = args
 107
 108     def elaborate(self, platform):
 109         m = Module()
 110         enc1, enc2 = self.encoder_cls(*self.coder_args), self.encoder_cls(*self.coder_args)
 111         m.submodules += enc1, enc2
 112         m.d.comb += [
 113             Assume(enc1.i + 1 == enc2.i),
 114             Assert(sum(enc1.o ^ enc2.o) == self.distance)
 115         ]
 116         return m
 117
 118
 119 class GrayCoderTestCase(FHDLTestCase):
 120     def test_reversible(self):
 121         spec = ReversibleSpec(encoder_cls=GrayEncoder, decoder_cls=GrayDecoder, args=(16,))
 122         self.assertFormal(spec, mode="prove")
 123
 124     def test_distance(self):
 125         spec = HammingDistanceSpec(distance=1, encoder_cls=GrayEncoder, args=(16,))
 126         self.assertFormal(spec, mode="prove")