Yet Another (Super) Chip 8 Emulator

Table of Contents

1. What is it?
2. License
3. Compiling
4. Running
   1. Requirements
   2. Starting the Emulator
   3. Running a ROM
   4. Screen Scale
   5. Execution Delay
   6. Trace Mode
   7. Step Mode
5. Keys
   1. Regular Keys
   2. Debug Keys
6. ROM Compatibility
7. Third Party Licenses and Attributions
   1. JCommander
   2. Apache Commons IO
   3. Vera Mono Font

What is it?

This project is a Chip 8 emulator written in Java. There are two other versions of the emulator written in different languages:

• Chip8Python
• Chip8C

The original goal of these projects was to learn how to code a simple emulator.

In addition to supporting Chip 8 ROMs, the emulator also supports the Super Chip 8 instruction set. Note that no additional configuration is needed to run a Super Chip 8 ROM - simply run the ROM the same way you would run a normal Chip 8 ROM.

License

This project makes use of an MIT license. Please see the file called LICENSE for more information. Note that this project may make use of other software that has separate license terms. See the section called Third Party Licenses and Attributions below for more information on those software components.

Compiling

To compile the project, you will need a Java Development Kit (JDK) version 8 or greater installed. Recently, Oracle has changed their license agreement to make personal and developmental use of their JDK free. However, some other use cases may require a paid subscription. Oracle's version of the JDK can be downloaded here. Alternatively, if you prefer to use a JRE with an open-source license (GPL v2 with Classpath Exception), you may visit https://adoptopenjdk.net and install the latest Java Development Kit (JDK) for your system. Again, JDK version 8 or better will work correctly.

To build the project, switch to the root of the source directory, and type:

./gradlew build

On Windows, switch to the root of the source directory, and type:

gradlew.bat build

The compiled JAR file will be placed in the build/libs directory, as a file called emulator-1.0.1-all.jar.

Running

Requirements

You will need a copy of the Java Runtime Environment (JRE) version 8 or greater installed in order to run the compiled JAR file. For most systems, you can install Java 8 JRE by visiting http://java.com and installing the Oracle Java Runtime Environment for your platform. This version of the JRE is free for personal use but contains a custom binary license from Oracle. Alternatively, if you prefer to use a JRE with an open-source license (GPL v2 with Classpath Exception), you may visit https://adoptopenjdk.net and install the latest Java Development Kit (JDK) for your system, which will include an appropriate JRE.

Starting the Emulator

By default, the emulator can start up without a ROM loaded. Simply double click the JAR file, or run it with the following command line:

java -jar emulator-1.0.1-all.jar

Running a ROM

The command-line interface currently requires a single argument, which is the full path to a Chip 8 ROM:

java -jar emulator-1.0.1-all.jar /path/to/rom/filename

This will start the emulator with the specified ROM.

Screen Scale

The --scale switch will scale the size of the window (the original size at 1x scale is 64 x 32):

java -jar emulator-1.0.1-all.jar /path/to/rom/filename --scale 10

The command above will scale the window so that it is 10 times the normal size.

Execution Delay

You may also wish to experiment with the --delay switch, which instructs the emulator to add a delay to every operation that is executed. For example,

java -jar emulator-1.0.1-all.jar /path/to/rom/filename --delay 10

The command above will add a 10 ms delay to every opcode that is executed. This is useful for very fast computers (note that it is difficult to find information regarding opcode execution times, as such, I have not attempted any fancy timing mechanisms to ensure that instructions are executed in a set amount of time).

Trace Mode

You can have the emulator to start in trace mode, where each instruction is disassembled and displayed in the bottom left hand corner of the screen on a semi-transparent overlay. To do this:

java -jar emulator-1.0.1-all.jar /path/to/rom/filename --trace

Trace mode can also be started at any time by pressing the X key. Pressing C or X will exit trace mode. Trace mode can also be accessed by clicking on CPU->Trace Mode.

Step Mode

You can have the emulator to start in step mode, where each instruction is disassembled and displayed in the bottom left hand corner of the screen on a semi-transparent overlay, and the next instruction will not be executed until the N key is pressed. To do this:

java -jar emulator-1.0.1-all.jar /path/to/rom/filename --step

Step mode can also be accessed by pressing the Z key. By pressing the N key, the emulator will execute the next instruction and again pause. Pressing the Z key will leave the emulator in trace mode, but will cause it to continue executing instructions as normal. Pressing C or Z will cancel step and trace modes, and cause it to continue executing instructions as normal. Step mode can also be accessed by clicking on CPU->Step Mode.

Keys

There are two sets of keys that the emulator uses: debug keys and regular keys.

Regular Keys

The original Chip 8 had a keypad with the numbered keys 0 - 9 and A - F (16 keys in total). Without any modifications to the emulator, the keys are mapped as follows:

Debug Keys

Pressing a debug key at any time will cause the emulator to enter into a different mode of operation. The debug keys are:

ROM Compatibility

Here are the list of public domain ROMs and their current status with the emulator.

Third Party Licenses and Attributions

JCommander

This links to the JCommander library, which is licensed under the Apache License, Version 2.0. The license can be downloaded from http://www.apache.org/licenses/LICENSE-2.0.html. The source code for this software is available from https://github.com/cbeust/jcommander

Apache Commons IO

This links to the Apache Commons IO, which is licensed under the Apache License, Version 2.0. The license can be downloaded from http://www.apache.org/licenses/LICENSE-2.0.html. The source code for this software is available from http://commons.apache.org/io

Vera Mono Font

This project includes an unmodified "Vera Mono" font under the following license agreement:

Copyright (c) 2003 by Bitstream, Inc. All Rights Reserved. Bitstream
Vera is a trademark of Bitstream, Inc.

Permission is hereby granted, free of charge, to any person obtaining
a copy of the fonts accompanying this license ("Fonts") and associated
documentation files (the "Font Software"), to reproduce and distribute
the Font Software, including without limitation the rights to use,
copy, merge, publish, distribute, and/or sell copies of the Font
Software, and to permit persons to whom the Font Software is furnished
to do so, subject to the following conditions:

The above copyright and trademark notices and this permission notice
shall be included in all copies of one or more of the Font Software
typefaces.

The Font Software may be modified, altered, or added to, and in
particular the designs of glyphs or characters in the Fonts may be
modified and additional glyphs or characters may be added to the
Fonts, only if the fonts are renamed to names not containing either
the words "Bitstream" or the word "Vera".

This License becomes null and void to the extent applicable to Fonts
or Font Software that has been modified and is distributed under the
"Bitstream Vera" names.

The Font Software may be sold as part of a larger software package but
no copy of one or more of the Font Software typefaces may be sold by
itself.

THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL
BITSTREAM OR THE GNOME FOUNDATION BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF THE USE OR INABILITY TO USE THE FONT
SOFTWARE OR FROM OTHER DEALINGS IN THE FONT SOFTWARE.

Except as contained in this notice, the names of Gnome, the Gnome
Foundation, and Bitstream Inc., shall not be used in advertising or
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or Bitstream Inc., respectively. For further information, contact:
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