Re: [stella] Supercharger BIN format

Subject: Re: [stella] Supercharger BIN format
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>
Date: Fri, 08 Jan 1999 16:39:26 +0100
At 22:49 07.01.99 -0500, you wrote:
>I thought I understood the 8448 file format of the Supercharger bins,
>however, it looks like I don't :-)  Does anyone have detailed information
>about the contents of these files?

The 8448 byte files are a cut down version of the 16 kb BINs on
the SC-CD. If you have this CD you can check Jim's source code to
see how they were created.

I think the file format is as follows:

The first 6 kb contain 24 pages of game data each 256 bytes long.
The pages don't have to be in order. Where they will be loaded to
in the Supercharger depends on the page header.

The next 2 kb are just filler data.

The file ends with 256 bytes of header information for the Supercharger:
   8 bytes of game header
   8 filler bytes
   24 byte page number table
   8 filler bytes
   24 byte page checksum table
   184 filler bytes

Game header:
-   start address low byte
-   start address high byte
-   RAM config byte
       D7-D5 write pulse delay
       D4-D2 bank config
          000  3  ROM
          001  1  ROM
          010  3   1
          011  1   3
          100  3  ROM
          101  2  ROM
          110  3   2
          111  2   3
       D1 write enable (1 enable; 0 disable)
       D0 ROM power (0 power on; 1 power off)
-   number of pages to load
-   checksum (the sum over all 8 game header bytes must be $55)
-   multi load index number
-   progress counter low byte
-   progress counter high byte

Page number table:
The page numbers get encoded like this [(page number -1)*4 modulo $1f].
If the 24 pages were transfered to the SC in order so that it would
load them from bank 1 byte 0 to bank 3 byte $7ff, the page number table
would look like this:

Page checksum table:
The sum over all 256 bytes in a page + the page number value + the
page checksum must be $55.

Ciao, Eckhard Stolberg

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