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e4a4a9800d
It's a bit more inconvenient in terms of register protection (BC is much more generally useful than IY), but it makes tight spots such as next and execute much faster, so I think it's worth it.
15 lines
409 B
Plaintext
15 lines
409 B
Plaintext
( Computes n into crc c with polynomial 0x1021 )
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CODE _crc16 ( c n -- c ) EXX, ( protect BC )
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HL POP, ( n ) DE POP, ( c )
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A L LDrr, D XORr, D A LDrr,
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B 8 LDri,
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BEGIN,
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E SLA, D RL,
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IFC, ( msb is set, apply polynomial )
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A D LDrr, 0x10 XORi, D A LDrr,
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A E LDrr, 0x21 XORi, E A LDrr,
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THEN,
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DJNZ, AGAIN,
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DE PUSH,
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EXX, ( unprotect BC ) ;CODE
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