Commodore 64: Rack-It Tape loader
Used on Hewsons "Rack It" label re-releases (maybe 1st releases too?) such as...
Cybernoid II, Gribblys Day Out & Steel.
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Threshold : $160 (352) clock cycles (TAP byte= $2C).
Bit 0 : $1D
Bit 1 : $3D
Endianess : MSbF
Pilot byte : varies, but these are found so far: $25, $de, $97 (usually around 220-260 of)
Sync : varies, but these are found so far: $3d, $14, $1b
Then...
1 byte : XOR cipher value for data, if $00 not enciphered at all
1 byte : Bank-value
1 byte : XOR checksum of data (header excluded)
2 bytes : End Address (MSBF)
2 bytes : Start Address (MSBF)
1 byte : File ID
n bytes : Data
Notes:
Pilot (p) & Sync (s) bytes differ between tapes...
Cybernoid 2.. p:$25, s:$3D.
Gribblys Day Out.. p:$DE, s:$14 (also for Gribblys Special Day Out).
Steel p:$97, s:$1B.
The pilots for rack-it blocks are often distorted at the beginning for first 200 pulses
or so, making it hard to know the exact quantity of pilot bytes.
256 is a good number to use when repairing.
After data blocks is usually 8 unused pulses, these are safe to remove if desired.
