mirror of
https://github.com/myhdl/myhdl.git
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95 lines
2.4 KiB
Python
95 lines
2.4 KiB
Python
from __future__ import generators
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import unittest
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from unittest import TestCase
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from myhdl import Simulation, Signal, delay, intbv, bin
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from bin2gray import bin2gray
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MAX_WIDTH = 11
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def nextLn(Ln):
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""" Return Gray code Ln+1, given Ln. """
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Ln0 = ['0' + codeword for codeword in Ln]
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Ln1 = ['1' + codeword for codeword in Ln]
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Ln1.reverse()
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return Ln0 + Ln1
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class TestOriginalGrayCode(TestCase):
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def testOriginalGrayCode(self):
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"""Check that the code is an original Gray code."""
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Rn = []
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def stimulus(B, G, n):
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for i in range(2**n):
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B.next = intbv(i)
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yield delay(10)
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Rn.append(bin(G, width=n))
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Ln = ['0', '1'] # n == 1
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for w in range(2, MAX_WIDTH):
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Ln = nextLn(Ln)
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del Rn[:]
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B = Signal(intbv(0)[w:])
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G = Signal(intbv(0)[w:])
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dut = bin2gray(B, G)
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stim = stimulus(B, G, w)
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sim = Simulation(dut, stim)
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sim.run(quiet=1)
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self.assertEqual(Ln, Rn)
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class TestGrayCodeProperties(TestCase):
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def testSingleBitChange(self):
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"""Check that only one bit changes in successive codewords."""
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def test(B, G):
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w = len(B)
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G_Z = Signal(intbv(0)[w:])
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B.next = intbv(0)
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yield delay(10)
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for i in range(1, 2**w):
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G_Z.next = G
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B.next = intbv(i)
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yield delay(10)
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diffcode = bin(G ^ G_Z)
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self.assertEqual(diffcode.count('1'), 1)
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self.runTests(test)
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def testUniqueCodeWords(self):
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"""Check that all codewords occur exactly once."""
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def test(B, G):
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w = len(B)
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actual = []
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for i in range(2**w):
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B.next = intbv(i)
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yield delay(10)
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actual.append(int(G))
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actual.sort()
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expected = list(range(2**w))
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self.assertEqual(actual, expected)
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self.runTests(test)
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def runTests(self, test):
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"""Helper method to run the actual tests."""
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for w in range(1, MAX_WIDTH):
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B = Signal(intbv(0)[w:])
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G = Signal(intbv(0)[w:])
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dut = bin2gray(B, G)
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check = test(B, G)
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sim = Simulation(dut, check)
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sim.run(quiet=1)
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if __name__ == '__main__':
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unittest.main()
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