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NGPC Dev Wiki

A developer reference for programming the Neo Geo Pocket Color (NGPC) and its TLCS-900/H CPU: hardware registers, graphics, audio, the CPU/toolchain, and reusable game-programming patterns. Hardware-focused and engine-agnostic — every page documents the machine and the techniques, not any single game or project.

Conventions: addresses are hex (0x8800), CPU is the Toshiba TLCS-900/H at 6.144 MHz, the display is 160×152 visible with 152 visible scanlines per frame at ~60 Hz.

Hardware

  • Hardware Registers — Complete register reference: CPU spec table, memory map, timers (prescaler/modes/Timer3-Z80), interrupts (with MicroDMA), OAM, tilemaps, audio, IRQ, and the critical hardware gotchas.
  • BIOS — BIOS calls (SWI), conventions, vectors, register bank 3, and the system library functions.

CPU and Toolchain

  • TLCS-900/H Reference — High-density CPU reference: registers, ABI / calling convention, data types, memory model, NGPC memory layout, opcode encoding, and the memory-form ALU encoding table.
  • Assembly — TLCS-900/H assembly: syntax, gotchas, LDIRW patterns, calling convention.
  • Build Toolchain — C compiler rules (C89, far pointers, volatile, ISR, inline ASM), memory model, the confirmed ABI, known compiler/linker bugs, and the CC900 toolchain internals (pipeline, TAC IR, runtime helpers, assembler/linker syntax).

Graphics

  • Graphics Overview — The K2GE graphics pipeline at a glance.
  • Sprites and OAM — OAM (0x8800), sprite palettes (0x8C00), metasprites, sprite budget, performance.
  • Tilemaps and Scrolling — SCR1/SCR2 scroll planes, tilemaps, scrolling, HUD-as-tilemap.
  • Colors and Palettes — Color/palette reference, indices, validation notes.
  • Effects and Raster — Raster/HBlank effects, palette FX, bitmap mode, text rendering, raster split performance.
  • DMA — DMA usage, MicroDMA, raster DMA, performance, pitfalls, and the inline-ASM DMA sequences.
  • VRAM Queue — Queued VRAM updates and the LDIRW copy contract.

Audio

  • Audio — Sound hardware, the audio driver, and playback patterns.

Systems

  • Game Loop — Main loop, VBlank sync, watchdog, frame budget, state-machine patterns.
  • Input — Joypad polling, edge detection, menu/game input.
  • Storage and Saves — Flash save and RTC, save struct design, and flash hardware pitfalls.
  • Collision — AABB and tile collision, shmup patterns, codegen pitfalls.
  • Fixed-Point Math — Fixed-point (8.4), LUTs, compression.
  • Localization — BIOS language detection (EN/JP), bilingual ROM, string tables, system font.
  • Debug Tools — On-device CPU profiler, ring-buffer log, runtime assert.

Pipeline and Patterns

  • Asset Pipeline — PNG export, compression, runtime loading.
  • Gameplay Patterns — State machines, pacing, and genre patterns (shmup, platformer, puzzle, grid, racing, adventure, roguelike/procedural dungeon).

Quick start by task

I want to… Start here
Look up a hardware register or the memory map Hardware Registers
Set up the build / understand the compiler Build Toolchain
Write or read TLCS-900/H assembly Assembly · TLCS-900/H Reference
Draw sprites / scroll a background Sprites and OAM · Tilemaps and Scrolling
Move data fast to VRAM DMA · VRAM Queue
Build a stable main loop Game Loop
Add save support Storage and Saves
Do a raster / HUD split Effects and Raster