# KSim65 - Kotlin/JVM 6502/65C02 microprocessor simulator

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

![6502](https://upload.wikimedia.org/wikipedia/commons/thumb/4/43/KL_MOS_6502.jpg/320px-KL_MOS_6502.jpg)

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 :-)
- simulates various hardware components (bus, cpu, memory, i/o controllers)
- IRQ and NMI
- instruction cycle times are simulated (however the *internal* cpu behavior is not cycle-exact for simplicity reasons)
- has all 6502 and 65c02 instructions, including many of the 'illegal' 6502 instructions (goal is 100% eventually)
- correct BCD mode for adc/sbc instructions on both cpu types
- passes several extensive unit test suites that verify instruction and cpu flags behavior
- simple debugging machine monitor, which basic disassembler and assembler functions
- provide a few virtual example machines, one of which is a fairly capable Commodore-64


## Documentation

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

## Using it as a library in your own project

Get it via the Jitpack.io repository that publishes builds based on Github releases.
See https://jitpack.io/#irmen/ksim65/


## 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:

![ehBasic](ehbasic.png)

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](http://vice-emu.sourceforge.net/).
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.

![C64 emulation](c64.png)


### License information

Ksim65 itself is licensed under the MIT software license, see file LICENSE.

It includes the 'Spleen' bitmap font (https://github.com/fcambus/spleen),
which has the following license (BSD):

Copyright (c) 2018-2020, Frederic Cambus
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS
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