68 lines
1.3 KiB
Python
68 lines
1.3 KiB
Python
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#!/usr/bin/python
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# produce a sync word for a given LAP
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lap = 0xffffff
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pn = 0x83848D96BBCC54FC
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# generator matrix for (64,30) linear block code
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# based on polynomial 0260534236651
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# (see gen_check_tables.py for automatic generation)
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g = (
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0x8000000000000001,
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0x40000002c2b89ed4,
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0x20000001615c4f6a,
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0x10000000b0ae27b5,
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0x080000029aef8d0e,
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0x040000014d77c687,
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0x0200000264037d97,
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0x01000003f0b9201f,
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0x008000033ae40edb,
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0x004000035fca99b9,
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0x002000036d5dd208,
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0x00100001b6aee904,
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0x00080000db577482,
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0x000400006dabba41,
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0x00020002f46d43f4,
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0x000100017a36a1fa,
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0x00008000bd1b50fd,
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0x000040029c3536aa,
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0x000020014e1a9b55,
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0x0000100265b5d37e,
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0x0000080132dae9bf,
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0x000004025bd5ea0b,
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0x00000203ef526bd1,
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0x000001033511ab3c,
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0x000000819a88d59e,
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0x00000040cd446acf,
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0x00000022a41aabb3,
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0x0000001390b5cb0d,
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0x0000000b0ae27b52,
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0x0000000585713da9)
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def encode(data):
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assert data < 2**30
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codeword = 0
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for i in range(30):
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if (data & (0x20000000 >> i)):
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codeword ^= g[i]
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return codeword
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# append barker code
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if (lap & 0x800000):
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data = 0x13000000 | lap
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else:
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data = 0x2c000000 | lap
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# scramble
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data ^= (pn >> 34)
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# encode
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codeword = encode(data)
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# scramble again
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syncword = codeword ^ pn
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print "0x%06x 0x%016x 0x%016x" % (lap, codeword, syncword)
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