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8bitworkshop/tools/lfsrcalc.py
2018-11-22 14:11:56 -05:00

31 lines
834 B
Python
Executable File

#!/usr/bin/python
MAXBITS=16
print("Period,nbits,feedback,mask")
for n in range(1,MAXBITS):
mask = (1<<n)-1
hibit = (1<<(n-1))
for i in range(0,1<<n):
for invert in [0,1]:
x = 1
seq = []
seen = set()
while x and not x in seen:
seq.append(x)
seen.add(x)
feedback = x & hibit
x = ((x << 1) & mask)
if invert:
if not feedback:
x ^= i
else:
if feedback:
x ^= i
if x:
seqindex = seq.index(x)
seqlen = len(seq) - seqindex
if seqlen>1:
print((seqlen, "#(%d,%d'%s,%d)" % (n,n,bin(i)[1:],invert), seqindex))