Part 2: Programming the X65 in 65816 Assembly

The second half of the book is dedicated to writing software for the X65 using 65816 assembly language. This section provides a structured learning path, covering everything from the basics of the instruction set to advanced optimization techniques. Topics include:

• Chapter 8: Introduction to 65816 Assembly
  • Overview of the 65C816 CPU
    • Key Features
    • Common Misunderstandings
    • Applications
  • Registers and Addressing Modes
    • Enhanced Register Set
      • Accumulator (A)
      • Index Registers (X and Y)
      • Direct Page Register (D)
      • Stack Pointer (S)
      • Program Bank Register (PBR)
      • Data Bank Register (DBR)
      • Processor Status Register (P)
    • Expanded Addressing Modes
      • 6502-Compatible Modes
      • New 65816-Specific Modes
    • Practical Usage of Registers
      • Accumulator Management
      • Index Register Techniques
      • Direct Page Utilization
      • Bank Register Management
  • Transitioning from 6502 to 65816
    • Key Differences for 6502 Programmers
      • Register Size Management
      • Memory Width Considerations
      • Stack Usage Differences
      • Direct Page vs. Zero Page
      • Handling 24-bit Addressing
    • Common Pitfalls When Transitioning
      • Register Width Confusion
      • Stack Pointer Assumptions
      • Bank Boundary Crossing
      • Direct Page Alignment Penalties
    • Leveraging 65816 Advantages
      • Block Move Instructions
      • 16-bit Arithmetic
      • Stack Frames for Subroutines
• Chapter 9: Development Environment Setup
  • Assembling and Linking with cc65
  • Using the X65 Emulator for Testing
  • Debugging Techniques and Tools
• Chapter 10: Memory Management
  • Utilizing the 16MB PSRAM
  • Direct Page and Stack Usage
• Chapter 11: Graphics Programming
  • Interfacing with CGIA
  • Display List
    • Overview of the CGIA Display List
    • Display List Instructions
      • Control Instructions (0-7)
      • Mode Row Instructions (8-F)
    • Using the Display List
  • Plane Registers Interpretation
    • Background Plane Registers
      • Background Plane Flags
    • HAM Mode Registers
    • Affine Transform Mode Registers
    • Sprite Plane Type Registers
  • Implementing HAM Mode Graphics
    • Hold-And-Modify (HAM) Mode
    • HAM Encoding Format
      • Commands
    • Rendering HAM Mode
    • Optimizing HAM Graphics
    • Applications of HAM Mode
  • Creating Mixed-Mode Display Lists
• Chapter 12: Sound Programming
  • Generating Audio with PWM Channels
  • FM Synthesis Basics
  • Programming the Yamaha SD-1 Synthesizer
  • Managing Audio Output through the Mixer
• Chapter 13: Input/Output Handling
  • Managing USB Devices via RP816-RIA
  • Networking with ESP32-C3
  • Reading Inputs from DE-9 Joysticks
• Chapter 14: Operating System
  • Features of OS/816
  • Hybrid Multitasking
  • Integrating the Monitor Console
  • Memory and Process Management
• Chapter 15: Advanced Programming Techniques
  • Optimizing Performance on the 65C816
  • Inline Assembly Practices
  • Utilizing the X65 Emulator for Development
• Chapter 16: Example Projects and Applications
  • “Hello, World!” (Text Output)
  • Developing a Simple Game
  • Creating Music with the SD-1
  • Networking Applications using ESP32-C3
• Chapter 17: Future Development and Community Contributions
  • Potential Hardware and Software Enhancements
  • Open-Source Contributions
  • Engaging with the X65 Community

Key Topics Covered

• An introduction to 65816 assembly syntax and structure

• Working with registers, addressing modes, and stack operations

• Handling memory efficiently in a flat 16MB address space

• Programming the graphics system using the display list

• Generating sound with the Yamaha SD-1 FM synthesizer

• Interfacing with peripherals and expansion hardware

• Optimizing code for performance and efficiency

By the end of Part 2, readers will have the knowledge required to develop software, games, and applications for the X65, as well as extend its capabilities through custom hardware and expansion modules.