Palace loader
=====================
  info by Fabrizio Gennari <fabrizio.ge@tiscalinet.it>

Used by Barbarian, Rimrunner, Antiriad...

Encoding:
---------
 Threshold: 469 clock cycles

Data Endianess: MOST Significant bit First

Structure:
----------
The header for bit synchronization is made by 
* a 1 bit
* 15 bytes with value $01
* an arbitrary sequence of bytes (that is, the loader accepts any sequence of bytes after the first fifteen 1's. In practical cases, there are all 1's)
* 4 bytes: the sequence $4A $50 $47 $29.

Then follows a series of 256-byte blocks, whose structure is like that:
* an arbitrary sequence of bytes (typically all $01)
* 4 bytes: the sequence $4A $50 $47 $10
* 1 byte: block number (first in the series is 0, then increments by 1)
* 256 bytes: data 
* 1 byte: the EOR checksum of the 256 data bytes.

Each block starts immediately after the previous one has finished (no bit resync between blocks) and are stored in memory one after the other (first byte of a block is stored just after last byte of previous block).

Before calling the loading routine, the caller fills locations $80 and $81 with the memory location (low byte, high byte) where to put the first byte of the first block, and location $101 with the total number of blocks in the series. After the series of blocks is loaded, a new bit resync is needed.
