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Merge pull request #13 from felixheld/crc_pythonize 

pythonize CRC calculation
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enjoy-digital 2018-02-22 09:00:25 +01:00 committed by GitHub
parent 8fc7161036 9dcc7bc65e
commit 4e08d6e9f9
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1 changed files with 5 additions and 4 deletions
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9
liteeth/core/mac/crc.py
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@ -40,8 +40,8 @@ class LiteEthMACCRCEngine(Module):
def _optimize_eq(l): def _optimize_eq(l):
""" """
Replace even numbers of XORs in the equation remove an even numbers of XORs with the same bit
with an equivalent XOR replace an odd number of XORs with a single XOR
""" """
d = OrderedDict() d = OrderedDict()
for e in l: for e in l:
@ -55,12 +55,13 @@ class LiteEthMACCRCEngine(Module):
r.append(key) r.append(key)
return r return r
# compute and optimize CRC's LFSR # compute and optimize the parallel implementation of the CRC's LFSR
taps = [x for x in range(width) if (1 << x) & polynom]
curval = [[("state", i)] for i in range(width)] curval = [[("state", i)] for i in range(width)]
for i in range(data_width): for i in range(data_width):
feedback = curval.pop() + [("din", i)] feedback = curval.pop() + [("din", i)]
for j in range(width-1): for j in range(width-1):
if (polynom & (1<<(j+1))): if j+1 in taps:
curval[j] += feedback curval[j] += feedback
curval[j] = _optimize_eq(curval[j]) curval[j] = _optimize_eq(curval[j])
curval.insert(0, feedback) curval.insert(0, feedback)