User:Zzo38/DotFami

This is a draft for .fami format of NES/Famicom ROM image files. This format allows title text, debugging information, custom mapper, and a few more.

(N.B. Do not delete or move this file until the draft is completed.)

Difference of this format with others includes:

• You can specify NTSC and PAL.
• Can include descriptive text.
• There is no fixed set of mapper numbers; instead the components of the cartridge are configured individually.
• Debugging symbols can be included.

File Order

• Header
• ROM data
• Mapper codes
• Symbol data
• Descriptive text

(Note: Sixteen bit numbers throughout the file are small-endian form.)

Header

  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|'F'|'A'|'M'|'I'|bnk|cpu| * | * |textLen|mapLen |symLen | * | * |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

• The first four bytes of the header must be the ASCII codes for "FAMI".
• bnk: Number ROM address lines (ROM size in bytes = two to power of this number).
• cpu: CPU mode flag:
  • bit0: Set if decimal mode should work.
  • bit1: Set if the 2A03 APU noise Mode flag should be ignored.
  • bit2-bit3: CPU clock speed multiplier: 00 = half speed, 01 = normal speed, 10 = double speed, 11 = quadruple speed.
  • bit4-bit5: TV system: 00 = perfect mode (RGB palette, NTSC timing, 32x30 tiles fully visible, no color artifacts), 01 = NTSC, 10 = PAL, 11 = work with NTSC or PAL.
  • bit6: Set if RAM should be initialized with random values instead of zero.
  • bit7: Set if mapper should be initialized with random values instead of zero.
• *: Reserved bytes; set to zero.
• textLen: Length of descriptive text.
• mapLen: Length of mapper codes.
• symLen: Length of symbol data.

Symbol Data

Symbol data consists of zero or more blocks consisting of a 16-bit ID followed by a 16-bit address followed by data.

The ID is formed as follows:

• bit0-bit5: Length of data (0 to 63 bytes).
• bit6-bit7: Mode (0=ROM, 1=mapper, 2=CPU memory, 3=extra)
• bit8-bit15: Depend on mode as follows:
  • 0: Bank number.
  • 1: Component ID.
  • 2: bit8=read, bit9=write, bit10=execute, bit11=16-bit data, bit12-bit15=reserved (set to zero).
  • 3: ID number of what kind of extra it is.

The extras would be:

• $00: Arcade cabinet switch. Bit0-bit2 of address is the switch number, bit8 of address is the default setting (1=on, 0=off). Data is the name of the switch.
• $01: Cartridge component name. Address bit0-bit7 = component ID, bit8-bit15 = sub-part. Data is name of component.
• $02: ASCII text. Address indicate what the text means: 0=title, 1=author, 2=copyright, 3=mapper name, 4=license, 5=publisher, 6=version, 7=date.
• $03: RGB palette. Address is from 0 to 63 indicating which palette index is used at first, data is the RGB triples (one byte per channel) starting from the specified palette index.
• $04: Track name. Address is track number (0 to 255 only). Data is the name of the track in ASCII text. Names can be blank, and if higher track number is given name but lower one is not, the lower numbered tracks still exist and have blank name. If this field is used, the initial value of accumulator is the track number to start at, and the mapper codes can also use the track number (which will not change at runtime unless the mapper code tells it to) to decide which ROM bank to enable and so on.