Programming guide

This programming guide is the complement to the NES reference guide. You will find more in-depth documentation about specific topics, tutorials on the most common problems encountered, a list of existing tools that will assist you during you development phase and more. If you're new to NES development, you should give a look to the "getting started" section first.

Getting started

• Before the basics
• Commissioning - suggestions for a non-programmer seeking help
• Programming Basics
• Installing CC65

General reference

• Registers
• Waiting for the PPU to power on
• CHR-ROM vs CHR-RAM and how to switch an NROM project from the former to the latter
• Emulation Libraries
• Catch-up technique used by emulators
• Flash Cartridges (PowerPak / Everdrive N8 / Everdrive N8 Pro / KrzysioCart)
• Music: Expansion audio
• Tools — includes assemblers, disassemblers, graphics, music/audio, and emulator-related utilities

Tutorials

• CPU basics
• PPU reference
• APU basics
• Compression
  • Fixed Bit Length Encoding
• Programming mappers
  • UNROM and UOROM
  • MMC1
• Programming Techniques
  • 6502 assembly optimisations
  • Cycle counting
  • RTS Trick
  • Jump Table
  • Scanning Tables
  • Scanning Large Tables
  • Synthetic Instructions
  • Programming with unofficial opcodes
  • Pointer tables
  • Multibyte constant
• Limitations
• Emulation Tutorials
• Sample RAM map
• PPU scrolling
  • How to scroll an infinite map
  • How to scroll with less artifact
  • How to split the screen for a status bar
  • How to do parallax scrolling with the scroll register
• Sprite size
• How to make raster effects by Bregalad
• The frame and NMIs by Disch
  • NMI thread: Make your status bar rock-solid
• Nerdy Nights sound
• Palette change mid frame
• Don't hardcode OAM addresses
• Interrupt forwarding
• Sprite cel streaming
• Drawing terrain
• Releasing on modern platforms

Libraries and samples

System

• Init code

Input

• Controller reading
• Controller reading code

Graphics

• Detecting video standard
• Placeholder graphics
• RLE decompression code for CHR by koitsu

Math

• Multiplication by a constant integer
• Fast signed multiply - Fast table driven multiplication
• 8-bit Multiply - Multiplies two 8-bit integers to a 16-bit result
• 8-bit Divide - Divide two 8-bit integers to a 16-bit result
• Division by a constant integer
• Divide by 3
• 16-bit BCD - An efficient 16-bit binary to decimal converter
• Base 100 - An alternate method of storing numbers, to simplify BCD conversion
• Random number generator

Audio

• APU period table
• Audio drivers
• Nerdtracker player in NESASM

Misc

• Skipping the FDS license screen
• CRC32 checksum calculation

Examples

• Projects - includes many useful open-source examples.
• Nerdy Nights Out (aka: Learning 6502) by BunnyBoy
• Programming NES Games in C by Shiru
• How to Program an NES game in C by dougeff
• Simple game and editing guide (in C)
• Project template by tepples
• Minimal NES example using ca65 by rainwarrior

Reverse engineered techniques

• Bad Apple video compression
• Codemasters tile compression
• Big Bird's Hide and Speak sample compression
• Battletoads text compression (Huffman coding)
• Rad Racer rendering

Useful reference materials

Books

• Cady, Fredrick M. (1997). Microcontrollers and Microcomputers: Principles of Software and Hardware Engineering. New York: Oxford University Press. ISBN 0-19-511008-0.
• Eyes, David; Lichty, Ron (1986). Programming the 65816 including the 6502, 65C02, and 65802. New York: Brady Books/Prentice Hall Press (Simon & Schuster, Inc). ISBN 0-89303-789-3. Rights later purchased by Western Design Center.
• Fernandez, Judi N. (1983). 6502 Assembly Language Programming (Self-teaching Guides). John Wiley & Sons Inc. ISBN 978-0471861201.
• Leventhal, Lance A. (1986). 6502 Assembly Language Programming 2nd Edition. Osborne/McGraw-Hill. ISBN 0-07-881216-X.
• Zaks, Rodnay (1983). Programming the 6502 (Fourth Edition). Sybex, Inc. ISBN 0-89588-135-7.
• Zaks, Rodnay (1982). Advanced 6502 Programming. Sybex, Inc. ISBN 0-89588-089-X.
• Zaks, Rodnay (1980). Programming the 6502 (Third Edition). Sybex, Inc. ISBN 0-89588-046-6.

Online

• Programming the 65816 (including the 6502, 65C02, and 65802) by Western Design Center
  1. Programmingthe65816_ProgManual.pdf — 54MBytes, created 2015/03/27.
     • This is a full scan of the original Eyes/Lichty book using full images for each page, with the added bonus of OCR being applied so that text is searchable and copy-paste-able. Accurate/reliable given the nature of the scan.
       • backup copy via Koitsu (primary)
       • backup copy via Koitsu (secondary)
  2. Programmanual.pdf (a.k.a. WDC65C816_Program_Manual.pdf) — 1.7MBytes, created 2007/04/16.
     • This is a "pure text" version of the Eyes/Lichty book, however it is rife with very dangerous typos (wrong opcodes, etc.) in many areas, and contains a large number of formatting/layout mistakes not present in the original book. Bill Mensch (6502/65C02/65816 architect/designer) confirmed these mistakes, stating WDC is in the process of fixing them. If at all possible, use the newer PDF mentioned above.
     • It is suspected that WDC has pulled this PDF entirely from their website, instead advocating purchasing a "redone" version of the Lichty/Eyes book via Amazon. Kindle and paperback versions are available, but I (Koitsu) have not reviewed it.

Links

• The infamous 6502.txt: allegedly complete info on the 6502 instructions
• Machine Language for Beginners: a 1983 introduction to 6502 assembly language