Action Replay cartridge loader
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  info by Fabrizio Gennari <fabrizio.ge@tiscalinet.it>

Used by the Action Replay cartridge to save freezed games.

Encoding:
---------

In the pilot tone, sync sequence and first bytes of header, pulses are like this:
 Threshold: $1D0 (464) clock cycles
 Bit 0: TAP byte $23
 Bit 1: TAP byte $53

Data Endianess: LEAST Significant bit First

 Lead-In :  a stream of 1's, typically about 2048 of them, followed by a single 0 bit
 Sync sequence:  $52, $42

Structure:
----------
 00-01 Complement of length of data (High, Low byte)
 02-03 Start Address of data        (High, Low byte)
 04    Checksum (XOR of all data bytes)
 05    discarded (typically $00)
 06    Low byte of threshold for data bytes
 07    discarded (typically $00)
 08    Data bytes

To calculate the number of data bytes, do 65536-complement of length. To calculate threshold for data bytes, do $100+low byte. There are two possibilities for the threshold: $1D0 (in that case, following pulses are identical to previous ones: this is the case of Turbo backup) and $111 (in that case, pulses are TAP bytes $13 for 0 and $2B for 1: that is the case of Superturbo backup)

