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124da6adec
Although the SPI Relay driver is RC2014-specific, the SD Card driver is generic enough to be a subsystem. That's the second subsystem we add and this warrants, I think, the formalization of a new concept: protocols.
16 lines
422 B
Plaintext
16 lines
422 B
Plaintext
( c n -- c )
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( Computes n into crc c with polynomial 0x09
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Note that the result is "left aligned", that is, that 8th
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bit to the "right" is insignificant (will be stop bit). )
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: _crc7
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XOR ( c )
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8 0 DO
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2 * ( <<1 )
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DUP 255 > IF
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( MSB was set, apply polynomial )
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0xff AND
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0x12 XOR ( 0x09 << 1, we apply CRC on high bits )
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THEN
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LOOP
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;
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