Diving into the realm of assembly language programming can feel like a leap into the unknown, but it's a journey that offers rich rewards. 6502 Assembly language, with its roots firmly embedded in the classic era of 8-bit microprocessors, provides an ideal starting point. In this first lesson, we'll familiarize ourselves with the basics of 6502 assembly and get started with our first simple program.
Understanding Assembly Language
Assembly language is a low-level programming language that correlates closely to machine language but employs more human-readable syntax. When programming in 6502 Assembly, you're interacting directly with the processor at a level that few high-level languages can rival.
The 6502 Processor
Famed for its use in systems like the Apple I, Apple II, and the original Nintendo Entertainment System, the 6502 microprocessor is an iconic piece of technology. Its design and instruction set make it an excellent introduction to assembly language programming.
6502 Assembly Syntax
6502 Assembly language syntax consists of opcodes (operation codes) that directly map to the processor's instruction set. Each opcode corresponds to a specific task, like loading a value into a register (LDA), storing it in memory (STA), or performing an operation like addition or subtraction (ADC, SBC).
Your First Program
Let's start with a simple program. This program will load a value into the accumulator, perform an addition, and then store the result in memory.
LDA #$01 ; Load the hexadecimal value 01 into the accumulator
ADC #$02 ; Add the hexadecimal value 02 to the accumulator
STA $0200 ; Store the accumulator's value in memory location $0200Assembling and Running Your Program
To convert your assembly code into machine code that the 6502 processor can understand, you'll need an assembler. There are several free options available online. After assembling your program, you can run it using a 6502 emulator.
Conclusion:
Welcome to the captivating world of 6502 Assembly programming! With this first simple program under your belt, you've taken the initial step into a broader universe of low-level programming. As we progress through these lessons, we'll explore more of the 6502's instruction set and capabilities, delving deeper into the intricacies of assembly programming. Keep experimenting, keep coding, and most importantly, enjoy the journey! Feel free to share your experience in the comments below as you embark on this exciting adventure.