KSim65 - Kotlin/JVM 6502/65C02 microprocessor simulator

Written by Irmen de Jong (irmen@razorvine.net)

Software license: MIT, see file LICENSE

This is a Kotlin/JVM library that simulates the 8-bit 6502 and 65C02 microprocessors, which became very popular in the the early 1980's.

Properties of this simulator:

• Written in Kotlin. It is low-level code, but hopefully still readable :-)
• Designed to simulate various hardware components (bus, cpu, memory, i/o controllers)
• IRQ and NMI simulation
• Aims to simulate correct instruction cycle timing, but is not 100% cycle exact for simplicity
• Aims to implements all 6502 and 65c02 instructions, including the 'illegal' 6502 instructions (not yet done)
• correct BCD mode for adc/sbc instructions on both cpu types
• passes several extensive unit test suites that verify instruction and cpu flags behavior
• provide a few virtual example machines, one of which is a Commodore-64

Documentation

Still to be written. For now, use the source ;-)

Virtual machine examples

Three virtual example machines are included. The default one starts with gradle run or run the ksim64vm command. There's another one ehBasicMain that is configured to run the "enhanced 6502 basic" ROM:

Finally there is a fairly functional C64 emulator running the actual roms (not included, but can be easily found elsewhere for example with the Vice emulator. The emulator supports character mode, bitmap mode (hires and multicolor), hardware sprites and various timers and IRQs. It's not cycle perfect, and the video display is drawn on a per-frame basis, so raster splits/rasterbars are impossible. But many other things work fine.