PAT file

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PAT files contain structured data to patch already loaded Z80 code. They're used to replace sound samples address tables originally loaded from Z80 files when different PCM files are loaded.

  • Maximum file size: 2048 bytes ?
  • Type code: 5
  • Loaded into: Z80 code RAM

Format

Blocks of 5 word (16 bit) values:

  • Patch address in bytes. $0000 means end of file. All the $0001~$FFFF range seems to work.
  • First data word is (/2), byteswapped and written to address
  • Second data word is (/2)-1, byteswapped written to address + 2
  • Third (optional) data word is (/2), byteswapped and written to address + 4
  • Fourth (optional) data word is (/2)-1, byteswapped written to address + 6

If the third data word is $0000, both the third and fourth patches are skipped.

Offset

When loading a PAT file (see loading files) the bank number and destination address parameters can be used to add an offset to all the patched values. This allows PCM data associated with a PAT file to be loaded into different regions of PCM DRAM without the need of multiple PAT files.

Code snippet from the TOP-SP1 system ROM which handles this:

C0BFAE  MOVEQ    #0x0,D0          Clear D0                 00000000
C0BFB0  MOVE.B   (0x7EDB,A5),D0   Bank number byte to D0   000000bb
C0BFB4  SWAP     D0                                        00bb0000  
C0BFB6  LSL.L    #4,D0                                     0bb00000
C0BFB8  OR.L     (0x7EF4,A5),D0   Insert destination addr. 0bbddddd
C0BFBC  LSR.L    #8,D0                                     000bbddd
C0BFBE  MOVE.W   D0,(0x7736,A5)   Offset will be:              bddd