PinMAME NVRAM Maps

The goal of this project is to document the contents of the .nv files PinMAME uses to store the contents of a game's non-volatile RAM. At a basic level, it's useful to know how a game stores its high scores so other programs (like a game launcher) can parse and display that information.

Going further and documenting adjustments and audits allows for the development of alternate interfaces (like a web browser) to view audits and change game settings without using the service menu.

This project started in October 2015, and should be considered "alpha" quality. As people map more games, the file format may change to support additional requirements.

I chose to use JSON as a simple yet flexible file format for this project. If necessary, other projects should be able to convert the map files to alternate formats. The JSON website describes the file format and includes links to parsing libraries in many programming languages.

Project home

License

This project is licensed under the GNU Lesser General Public License v3.0 (LGPL). LGPL requires that derived works be licensed under the same license, but works that only link to it do not fall under this restriction.

My intent is for the map files (.nv.json) to remain open and for everyone to benefit from updates, yet allow for their use in closed-source projects with attribution. Please include a GitHub link to the original project (or your fork of it), along with the description, "This program makes use of content from the PinMAME NVRAM Maps project."

Sample Code

My preference is to keep this project dedicated to just the JSON files so other projects can incorporate it as a git submodule.

A related project currently includes a Python program (nvram_parser.py) that works as a standalone application to dump a parsed .nv file, or as a class (ParseNVRAM) you can use from other programs.

Mapping New Games

Start PinMAME and write down all the high scores, and then exit. Open the game's .nv file in a hex editor and search for the initials. It should be possible to find each set of initials, with the corresponding score nearby.

For adjustments, make a list of each setting, its default value, the range of accepted values, and whether certain values have special meaning (like OFF or DISABLED). I make use of a modified version of PinMAME that monitors an address range and dumps any changes it detects to that range. It's a simple matter to change a setting and see the modified location in the NVRAM file.

Audits are a bit more difficult, and I intend to build a tool to modify portions of the NVRAM file to aid in matching audits to file locations. Setting each 6-byte grouping to its starting address should allow for quickly mapping each audit.

File Format

The JSON file is essentially a big dictionary or associative array, with the following key/value pairs. It may help to review one or more of the included files as an example of the file format while reading this section of the documentation.

In cases where this specification isn't clear, please use existing maps or the nvram_parser.py sample as a guide.

Numbers can appear as decimal values (1234) or hexadecimal values inside of strings ("0x4D2"). Most map files will only use hex for file offsets.

Meta Data

Note that keys starting with underscore describe the file itself, and not the contents of the corresponding NVRAM file.

• _roms (required): A list of PinMAME ROMs that use this map.
• _fileformat (required): A float indicating the file format's version. See Version History at the end of this file for changes.
• _version (required): A float indicating the JSON file's version.
• _copyright: Original author of the file, possibly a list of people who have contributed to the file.
• _license: All files from this project are covered by the LGPL license. Modified map files, or maps created using an existing map as a starting point are also covered by that license.
• _notes: Notes about the file, possibly indicating who created it or portions of the file that may not be entirely correct.
• _endian: Default endian setting for all entries in the file. Defaults to true.
• _char_map: Characters to use for the ch encoding instead of a straight ASCII table. See Whirlwind (whirl_l3.nv.json) as an example.

Descriptors

The map file contains objects describing sections of the .nv file and how to interpret them. They're comprised of the following key/value pairs:

• label: A label describing this collection of bytes in the .nv file.
• short_label: An optional, abbreviated label for use when space is limited (like in a game launcher on a DMD).
• encoding (required): One of the following:
  • "enum": An enumerated type where the byte at start is used as an index into a list of strings provided in values.
  • "int": A (possibly) multibyte integer, where each byte is multiplied by a power of 256. The byte sequence 0x12 0x34 would translate to the decimal value 4660.
  • "bits": Same decoding as "int", but used to sum select integers from the list in values.
  • "bcd": A binary-coded decimal value, where each byte represents two decimal digits of a number. The byte sequence 0x12 0x34 would translate to the decimal value 1234.
  • "ch": A sequence of 7-bit ASCII characters. If the JSON file has a _char_map key, use bytes from the NV file as indexes into that string instead of interpreting them as 7-bit ASCII.
  • "raw": A series of raw bytes, useful for extracting data yet to be decoded or that requires custom processing.
  • "wpc_rtc": A special type for a real-time clock value from a WPC game, stored as a sequence of 7 bytes. Starts with a two-byte year (2015 is 0x07 0xDF), month (1-12), day of month (1-31), day of the week (0-6, 0=Sunday), hour (0-23) and minute (0-59).
• You must specify the location of data in the file using one or more of the following directives:
  • start: Offset into the .nv file of the first byte to interpret. Default behavior is to use that single byte unless the end or length keys are present. Either start or offsets are required.
  • end: Offset into the file of the last byte to interpret. Its value must be greater than or equal to start.
  • length: Number of bytes to interpret, must be at least 1 (default).
  • offsets: Alternative to using start/end or start/length when bytes aren't contiguous. List of offsets to use. Either start or offsets are required.
• min and max: Used for adjustments to specify the valid range of values.
• default: Used for adjustments to specify the factory default value. Used for the initials entry of a high score to indicate the value for an empty entry (e.g., " " on WPC, "\u0000\u0000\u0000" on Gottlieb System 80). Defaults to 0 unless specified.
• values: A list of strings used for the enum encoding, starting at index 0. Also used for the bits encoding, as values for bit 0, 1, 2, etc.
• special_values: A set of key/value pairs for numeric field where some values have special meaning (for example, {"0": "OFF"}).
• units: Used to indicate that a field contains a time value as either a number of "seconds" or "minutes", and should be displayed as HH:MM:SS.
• suffix: A string to append to the value (e.g., "M" if the value represents millions).
• scale: A numeric multiplier for a decoded int, bcd, or bits.
• offset: A numeric value to add to a decided int, bcd, or bits value before displaying it. Applied after scale.
• mask: A mask to apply to each byte before processing. For example, a mask of "0x5F" converts lowercase initials to uppercase and a mask of "0x0F" clears the upper four bits.
• nibble: Replacement for packed attribute for ch and bcd types. Defaults to both (previously packed=true) indicating use of the full 8 bits/byte. Set to low (previously packed=false) to use the lower 4 bits of the byte or high to use the upper 4 bits of the byte. The bcd sequence 0x12 0x34 0x56 translates to 123456 when nibble is both, 246 when nibble is low and 135 when nibble is high. Robowars has an example of a nibble=low ch field, where the sequence 0x04 0x01 0x04 0x02 0x04 0x03 translates to 0x41 0x42 0x43 which is the string "ABC". Stern Dracula and Wild Fyre (identical ROM) have examples of nibble=high.
• packed: Deprecated in favor of nibble. Remove packed=true and replace packed=false with nibble=low.
• _note: A note for someone maintaining the file; not displayed when processing an NVRAM file.

File Map

Keys that don't start with an underscore typically have groups of descriptors as their values.

• endian: Set to either "big" or "little" to indicate the byte order of multibyte values in the ROM file. Defaults to "big".
• last_played: A descriptor (likely with a wpc_rtc encoding) with a date stamp of when PinMAME last saved the file.
• last_game: An array of up to four descriptors representing scores of the last game played on the machine. A score of 0 indicates that the game had less than four players.
• high_scores: The traditional high score table that would usually start with the Grand Champion and then proceed through First Place to Fourth Place. An array of objects with the following key/value pairs:
  • label: A label describing the score (e.g., "Grand Champion").
  • short_label: An abbreviated label (e.g., "GC").
  • initials: Descriptor of where the high score's initials are stored in the file.
  • score: Descriptor of where the high score's score is stored in the file.
• mode_champions: Another array of descriptors with recognition of other in-game accomplishments.
• adjustments: An object of key/value pairs for groupings of adjustments, where the key describes the group (e.g. "A.1 Standard Adjustments") and the value is another object of key/value pairs for that grouping. In that inner object, the keys are typically the numbers from the service menu ("01") and the values are the corresponding descriptor.
• audits: Same as adjustments, but for the game's audits (also referred to as "Bookkeeping").
• game_state: A collection of memory areas used during a game to store the state of the game (e.g., player #, ball #, progressive jackpot value, etc.) Not useful for PinMAME's .nv files, but could be referenced with custom code inside PinMAME. See the High Speed map for an example.

Checksums

The objects used for the last two entries in the file are slightly different from the other descriptors. They have the required start field, require either an end (preferred) or length, and label is optional. They introduce an optional groupings key used to treat a single descriptor as a list of equally-sized groupings.

(On WPC games, the audits are a series of 6-byte entries, each with an 8-bit checksum as the last byte.)

• checksum8: An array of memory regions protected by an 8-bit checksum. The last byte of the range is set so that the low byte from the sum of all bytes in the range is 0xFF.
• checksum16: An array of memory regions protected by a 16-bit checksum. That last two bytes of the range are set so that adding all other bytes in the range results in a value of 0xFFFF.

Version History

• v0.1: Initial Version
• v0.2: Deprecate packed attribute in favor of nibble.