emulator: PD777
type: libretro
core_classification: community_fork
source: "https://github.com/mittonk/PD777"
upstream: "https://github.com/W88DodPECuThLOl/PD777"
profiled_date: "2026-03-24"
core_version: "v1.0.0"
display_name: "Epoch - Cassette Vision (PD777)"
cores:
  - pd777
systems:
  - epochcv

notes: |
  PD777 is an Epoch Cassette Vision emulator (NEC uPD777C CPU), by
  W88DodPECuThLOl. Libretro port by Ken Mitton (mittonk).

  No BIOS or firmware files required. The .info file declares firmware_count = 0.

  Game loading in source/libretro/libretro.cpp:retro_load_game() (line 404-532).
  The core loads a code ROM file (.bin777) directly from the content path, then
  attempts to load a pattern ROM file (.ptn777) by replacing the extension.

  If neither file is found, the core falls back to hardcoded ROM data compiled
  from source/core/rom.cpp (Battle Vader program + pattern ROM dumps from
  oguchi-rd.com).

  The code ROM supports three formats:
    - Raw order: exactly 0xF00 bytes, program words in sequential address order
    - Raw address: address/data pairs (compiled-in rawRom[] array)
    - Formatted: header starting with "_CassetteVision_000" magic, version 0 or 1,
      includes key mapping, title, and code section at offset 0x100

  The pattern ROM supports three formats:
    - Formatted: 0x340 bytes, header "*CassetteVision*0000", 7x7 + 8x7 CG patterns
    - Raw bitstream: 0x4D0 bytes, bit-packed 7x7 and 8x7 character patterns
    - Built-in: fallback to patternRom[] / patternRom8[] arrays in rom.cpp

  The system directory path is retrieved via RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY
  but is not used for any file loading.

  Game identification uses a checksum over the loaded ROM to detect known cassettes
  (Battle Vader, Galaxian, etc.) and apply per-game key mappings and bent character
  tables. 11 cassette IDs are recognized (1-9, 11, 12).

  Supported extensions: zip, bin777, ptn777.

files: []

platform_details:
  cpu: "NEC uPD777C (uPD774 variant)"
  system: "Epoch Cassette Vision (1981)"
  region: "Japan"
  notes: |
    The Cassette Vision uses a NEC uPD777C (or uPD774 variant) as its main
    processor. Program ROM and pattern/character ROM are per-cartridge, not
    system-level. There is no system BIOS - the CPU executes directly from
    the cartridge ROM.

    The emulator supports analog paddles (4 paddles mapped to 2 analog sticks),
    lever switches, push buttons, course switch, and a lightgun peripheral.