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Reference.html
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<!-- saved from url=(0048)http://devernay.free.fr/hacks/chip8/C8TECH10.HTM -->
<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Cowgod's Chip-8 Technical Reference</title>
<style type="text/css"></style></head>
<body bgcolor="#FFFFFF" text="#000000" link="#0000FF" alink="#00007F" vlink="#7F7F7F">
<center>
Cowgod's<br>
<font size="7"><strong><tt>Chip-8</tt></strong></font><br>
Technical Reference v1.0<br>
</center>
<br>
<font size="4"><strong><em><u>
<a name="0.0">0.0</a> - Table of Contents <br>
</u></em></strong></font>
<br>
<tt><font size="3">
<strong><a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">0.0</a> - Table of Contents</strong><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.1">0.1</a> - Using This Document<br>
<br>
<strong><a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#1.0">1.0</a> - About Chip-8</strong><br>
<br>
<strong><a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.0">2.0</a> - Chip-8 Specifications</strong><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.1">2.1</a> - Memory<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#memmap">Diagram</a> - Memory Map<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.2">2.2</a> - Registers<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.3">2.3</a> - Keyboard<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#keyboard">Diagram</a> - Keyboard Layout<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.4">2.4</a> - Display<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#dispcoords">Diagram</a> - Display Coordinates<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#font">Listing</a> - The Chip-8 Hexadecimal Font<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.5">2.5</a> - Timers & Sound<br>
<br>
<strong><a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#3.0">3.0</a> - Chip-8 Instructions</strong><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#3.1">3.1</a> - Standard Chip-8 Instructions<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00E0">00E0</a> - CLS<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00EE">00EE</a> - RET<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0nnn">0<em>nnn</em></a> - SYS <em>addr</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#1nnn">1<em>nnn</em></a> - JP <em>addr</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2nnn">2<em>nnn</em></a> - CALL <em>addr</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#3xkk">3<em>xkk</em></a> - SE V<em>x</em>, <em>byte</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#4xkk">4<em>xkk</em></a> - SNE V<em>x</em>, <em>byte</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#5xy0">5<em>xy</em>0</a> - SE V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#6xkk">6<em>xkk</em></a> - LD V<em>x</em>, <em>byte</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#7xkk">7<em>xkk</em></a> - ADD V<em>x</em>, <em>byte</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy0">8<em>xy</em>0</a> - LD V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy1">8<em>xy</em>1</a> - OR V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy2">8<em>xy</em>2</a> - AND V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy3">8<em>xy</em>3</a> - XOR V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy4">8<em>xy</em>4</a> - ADD V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy5">8<em>xy</em>5</a> - SUB V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy6">8<em>xy</em>6</a> - SHR V<em>x</em> {, V<em>y</em>}<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy7">8<em>xy</em>7</a> - SUBN V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xyE">8<em>xy</em>E</a> - SHL V<em>x</em> {, V<em>y</em>}<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#9xy0">9<em>xy</em>0</a> - SNE V<em>x</em>, V<em>y</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Annn">A<em>nnn</em></a> - LD I, <em>addr</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Bnnn">B<em>nnn</em></a> - JP V0, <em>addr</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Cxkk">C<em>xkk</em></a> - RND V<em>x</em>, <em>byte</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Dxyn">D<em>xyn</em></a> - DRW V<em>x</em>, V<em>y</em>, <em>nibble</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Ex9E">E<em>x</em>9E</a> - SKP V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#ExA1">E<em>x</em>A1</a> - SKNP V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx07">F<em>x</em>07</a> - LD V<em>x</em>, DT<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx0A">F<em>x</em>0A</a> - LD V<em>x</em>, K<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx15">F<em>x</em>15</a> - LD DT, V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx18">F<em>x</em>18</a> - LD ST, V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx1E">F<em>x</em>1E</a> - ADD I, V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx29">F<em>x</em>29</a> - LD F, V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx33">F<em>x</em>33</a> - LD B, V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx55">F<em>x</em>55</a> - LD [I], V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx65">F<em>x</em>65</a> - LD V<em>x</em>, [I]<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#3.2">3.2</a> - Super Chip-48 Instructions<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00Cn">00C<em>n</em></a> - SCD <em>nibble</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00FB">00FB</a> - SCR<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00FC">00FC</a> - SCL<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00FD">00FD</a> - EXIT<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00FE">00FE</a> - LOW<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00FF">00FF</a> - HIGH<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Dxy0">D<em>xy</em>0</a> - DRW V<em>x</em>, V<em>y</em>, 0<br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx30">F<em>x</em>30</a> - LD HF, V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx75">F<em>x</em>75</a> - LD R, V<em>x</em><br>
<a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#Fx85">F<em>x</em>85</a> - LD V<em>x</em>, R<br>
<br>
<strong><a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#4.0">4.0</a> - Interpreters</strong><br>
<br>
<strong><a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#5.0">5.0</a> - Credits</strong><br>
</font></tt>
<br>
<br>
<font size="3"><strong><em><u>
<a name="0.1">0.1</a> - Using This Document
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
While creating this document, I took every effort to try to make it easy to read, as
well as easy to find what you're looking for.<br>
<br>
In most cases, where a hexadecimal value is given, it is followed by the equivalent
decimal value in parenthesis. For example, "0x200 (512)."<br>
<br>
In most cases, when a word or letter is italicized, it is referring to a variable
value, for example, if I write "V<em>x</em>," the <em>x</em> reffers to a 4-bit
value.<br>
<br>
The most important thing to remember as you read this document is that every <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a>
link will take you back to the Table Of Contents. Also, links that you have not yet visited
will appear in <font color="#0000FF">blue</font>, while links you have used will be
<font color="#7F7F7F">gray</font>.<br>
</font></tt>
<br>
<br>
<font size="4"><strong><em><u>
<a name="1.0">1.0</a> - About Chip-8
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
Whenever I mention to someone that I'm writing a Chip-8 interpreter, the response
is always the same: "What's a Chip-8?"<br>
<br>
Chip-8 is a simple, interpreted, programming language which was first used on some
do-it-yourself computer systems in the late 1970s and early 1980s. The COSMAC VIP,
DREAM 6800, and ETI 660 computers are a few examples. These computers typically
were designed to use a television as a display, had between 1 and 4K of RAM, and
used a 16-key hexadecimal keypad for input. The interpreter took up only
512 bytes of memory, and programs, which were entered into the computer in
hexadecimal, were even smaller.<br>
<br>
In the early 1990s, the Chip-8 language was revived by a man named Andreas
Gustafsson. He created a Chip-8 interpreter for the HP48 graphing calculator,
called Chip-48. The HP48 was lacking a way to easily make fast games at the time,
and Chip-8 was the answer. Chip-48 later begat Super Chip-48, a modification of
Chip-48 which allowed higher resolution graphics, as well as other graphical
enhancements.<br>
<br>
Chip-48 inspired a whole new crop of Chip-8 interpreters for various platforms,
including MS-DOS, Windows 3.1, Amiga, HP48, MSX, Adam, and ColecoVision. I became
involved with Chip-8 after stumbling upon Paul Robson's interpreter on the
World Wide Web. Shortly after that, I began writing my own Chip-8 interpreter.<br>
<br>
This document is a compilation of all the different sources of information I used
while programming my interpreter.<br>
</font></tt>
<br>
<br>
<font size="4"><strong><em><u>
<a name="2.0">2.0</a> - Chip-8 Specifications
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
This section describes the Chip-8 memory, registers, display, keyboard, and timers.<br>
</font></tt>
<br>
<br>
<font size="3"><strong><em><u>
<a name="2.1">2.1</a> - Memory
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
The Chip-8 language is capable of accessing up to 4KB (4,096 bytes) of RAM, from
location 0x000 (0) to 0xFFF (4095). The first 512 bytes, from 0x000 to 0x1FF, are
where the original interpreter was located, and should not be used by programs.<br>
<br>
Most Chip-8 programs start at location 0x200 (512), but some begin at 0x600 (1536).
Programs beginning at 0x600 are intended for the ETI 660 computer.<br>
<br>
<a name="memmap"><strong>Memory</strong></a><strong> Map:</strong><br>
+---------------+= 0xFFF (4095) End of Chip-8 RAM<br>
| |<br>
| |<br>
| |<br>
| |<br>
| |<br>
| 0x200 to 0xFFF|<br>
| Chip-8 |<br>
| Program / Data|<br>
| Space |<br>
| |<br>
| |<br>
| |<br>
+- - - - - - - -+= 0x600 (1536) Start of ETI 660 Chip-8 programs<br>
| |<br>
| |<br>
| |<br>
+---------------+= 0x200 (512) Start of most Chip-8 programs<br>
| 0x000 to 0x1FF|<br>
| Reserved for |<br>
| interpreter |<br>
+---------------+= 0x000 (0) Start of Chip-8 RAM<br>
</font></tt>
<br>
<br>
<font size="3"><strong><em><u>
<a name="2.2">2.2</a> - Registers
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
Chip-8 has 16 general purpose 8-bit registers, usually referred to as
V<em>x</em>, where <em>x</em> is a hexadecimal digit (0 through F). There is also
a 16-bit register called I. This register is generally used to store
memory addresses, so only the lowest (rightmost) 12 bits are usually used.<br>
<br>
The VF register should not be used by any program, as it is used as a flag by
some instructions. See section 3.0, <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#3.0">Instructions</a>
for details.<br>
<br>
Chip-8 also has two special purpose 8-bit registers, for the delay and sound timers.
When these registers are non-zero, they are automatically decremented at a rate
of 60Hz. See the section 2.5, <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.5">Timers & Sound</a>, for more
information on these.<br>
<br>
There are also some "pseudo-registers" which are not accessable from Chip-8
programs. The program counter (PC) should be 16-bit, and is used to store the
currently executing address. The stack pointer (SP) can be 8-bit, it is used to
point to the topmost level of the stack.<br>
<br>
The stack is an array of 16 16-bit values, used to store the address that
the interpreter shoud return to when finished with a subroutine. Chip-8 allows
for up to 16 levels of nested subroutines.<br>
</font></tt>
<br>
<br>
<font size="3"><strong><em><u>
<a name="2.3">2.3</a> - Keyboard
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
<a name="keyboard">The</a> computers which originally used the Chip-8 Language had a 16-key hexadecimal
keypad with the following layout:<br>
<br>
<table border="1" cellpadding="3" cellspacing="0" align="center">
<tbody><tr><td><tt>1</tt></td><td><tt>2</tt></td><td><tt>3</tt></td><td><tt>C</tt></td></tr>
<tr><td><tt>4</tt></td><td><tt>5</tt></td><td><tt>6</tt></td><td><tt>D</tt></td></tr>
<tr><td><tt>7</tt></td><td><tt>8</tt></td><td><tt>9</tt></td><td><tt>E</tt></td></tr>
<tr><td><tt>A</tt></td><td><tt>0</tt></td><td><tt>B</tt></td><td><tt>F</tt></td></tr>
</tbody></table>
<br>
This layout must be mapped into various other configurations to fit the keyboards
of today's platforms.<br>
</font></tt>
<br>
<br>
<font size="3"><strong><em><u>
<a name="2.4">2.4</a> - Display
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
<a name="dispcoords">The</a> original implementation of the Chip-8 language used a 64x32-pixel monochrome display
with this format:<br>
<br>
<table border="1" width="128" height="64" cellpadding="0" cellspacing="0" align="center">
<tbody><tr><td>
<table border="0" height="60" width="100%">
<tbody><tr><td valign="top" align="left">(0,0)</td><td valign="top" align="right">(63,0)</td></tr>
<tr><td valign="bottom" align="left">(0,31)</td><td valign="bottom" align="right">(63,31)</td></tr>
</tbody></table>
</td></tr>
</tbody></table>
<br>
Some other interpreters, most notably the one on the ETI 660, also had 64x48 and
64x64 modes. To my knowledge, no current interpreter supports these modes. More
recently, Super Chip-48, an interpreter for the HP48 calculator, added a
128x64-pixel mode. This mode is now supported by most of the interpreters on other
platforms.<br>
<br>
Chip-8 draws graphics on screen through the use of sprites. A sprite is a group
of bytes which are a binary representation of the desired picture. Chip-8 sprites
may be up to 15 bytes, for a possible sprite size of 8x15.<br>
<br>
Programs may also refer to a group of sprites representing the hexadecimal
digits 0 through F. These sprites are 5 bytes long, or 8x5 pixels. The data
should be stored in the interpreter area of Chip-8 memory (0x000 to 0x1FF).
Below is a listing of each character's bytes, in binary and hexadecimal:<br>
<br>
<a name="font"> </a>
<table align="center">
<tbody><tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"0"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* *<br>
* *<br>
* *<br>
****<br>
</tt></td>
<td><tt>
11110000<br>
10010000<br>
10010000<br>
10010000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x90<br>
0x90<br>
0x90<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"1"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
* <br>
** <br>
* <br>
* <br>
***<br>
</tt></td>
<td><tt>
00100000<br>
01100000<br>
00100000<br>
00100000<br>
01110000<br>
</tt></td>
<td><tt>
0x20<br>
0x60<br>
0x20<br>
0x20<br>
0x70<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
<tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"2"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
*<br>
****<br>
* <br>
****<br>
</tt></td>
<td><tt>
11110000<br>
00010000<br>
11110000<br>
10000000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x10<br>
0xF0<br>
0x80<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"3"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
*<br>
****<br>
*<br>
****<br>
</tt></td>
<td><tt>
11110000<br>
00010000<br>
11110000<br>
00010000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x10<br>
0xF0<br>
0x10<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
<tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"4"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
* *<br>
* *<br>
****<br>
*<br>
*<br>
</tt></td>
<td><tt>
10010000<br>
10010000<br>
11110000<br>
00010000<br>
00010000<br>
</tt></td>
<td><tt>
0x90<br>
0x90<br>
0xF0<br>
0x10<br>
0x10<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"5"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* <br>
****<br>
*<br>
****<br>
</tt></td>
<td><tt>
11110000<br>
10000000<br>
11110000<br>
00010000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x80<br>
0xF0<br>
0x10<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
<tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"6"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* <br>
****<br>
* *<br>
****<br>
</tt></td>
<td><tt>
11110000<br>
10000000<br>
11110000<br>
10010000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x80<br>
0xF0<br>
0x90<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"7"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
*<br>
* <br>
* <br>
* <br>
</tt></td>
<td><tt>
11110000<br>
00010000<br>
00100000<br>
01000000<br>
01000000<br>
</tt></td>
<td><tt>
0xF0<br>
0x10<br>
0x20<br>
0x40<br>
0x40<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
<tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"8"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* *<br>
****<br>
* *<br>
****<br>
</tt></td>
<td><tt>
11110000<br>
10010000<br>
11110000<br>
10010000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x90<br>
0xF0<br>
0x90<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"9"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* *<br>
****<br>
*<br>
****<br>
</tt></td>
<td><tt>
11110000<br>
10010000<br>
11110000<br>
00010000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x90<br>
0xF0<br>
0x10<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
<tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"A"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* *<br>
****<br>
* *<br>
* *<br>
</tt></td>
<td><tt>
11110000<br>
10010000<br>
11110000<br>
10010000<br>
10010000<br>
</tt></td>
<td><tt>
0xF0<br>
0x90<br>
0xF0<br>
0x90<br>
0x90<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"B"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
*** <br>
* *<br>
*** <br>
* *<br>
*** <br>
</tt></td>
<td><tt>
11100000<br>
10010000<br>
11100000<br>
10010000<br>
11100000<br>
</tt></td>
<td><tt>
0xE0<br>
0x90<br>
0xE0<br>
0x90<br>
0xE0<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
<tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"C"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* <br>
* <br>
* <br>
****<br>
</tt></td>
<td><tt>
11110000<br>
10000000<br>
10000000<br>
10000000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x80<br>
0x80<br>
0x80<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"D"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
*** <br>
* *<br>
* *<br>
* *<br>
*** <br>
</tt></td>
<td><tt>
11100000<br>
10010000<br>
10010000<br>
10010000<br>
11100000<br>
</tt></td>
<td><tt>
0xE0<br>
0x90<br>
0x90<br>
0x90<br>
0xE0<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
<tr>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"E"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* <br>
****<br>
* <br>
****<br>
</tt></td>
<td><tt>
11110000<br>
10000000<br>
11110000<br>
10000000<br>
11110000<br>
</tt></td>
<td><tt>
0xF0<br>
0x80<br>
0xF0<br>
0x80<br>
0xF0<br>
</tt></td>
</tr>
</tbody></table>
</td>
<td>
<table border="1" cellpadding="3" cellspacing="0">
<tbody><tr><td>"F"</td><td>Binary</td><td>Hex</td></tr>
<tr>
<td><tt>
****<br>
* <br>
****<br>
* <br>
* <br>
</tt></td>
<td><tt>
11110000<br>
10000000<br>
11110000<br>
10000000<br>
10000000<br>
</tt></td>
<td><tt>
0xF0<br>
0x80<br>
0xF0<br>
0x80<br>
0x80<br>
</tt></td>
</tr>
</tbody></table>
</td>
</tr>
</tbody></table>
</font></tt>
<br>
<br>
<font size="3"><strong><em><u>
<a name="2.5">2.5</a> - Timers & Sound
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
Chip-8 provides 2 timers, a delay timer and a sound timer.<br>
<br>
The delay timer is active whenever the delay timer register (DT) is non-zero.
This timer does nothing more than subtract 1 from the value of DT at a rate
of 60Hz. When DT reaches 0, it deactivates.<br>
<br>
The sound timer is active whenever the sound timer register (ST) is non-zero.
This timer also decrements at a rate of 60Hz, however, as long as ST's value is
greater than zero, the Chip-8 buzzer will sound. When ST reaches zero, the sound
timer deactivates.<br>
<br>
The sound produced by the Chip-8 interpreter has only one tone. The frequency
of this tone is decided by the author of the interpreter.<br>
</font></tt>
<br>
<br>
<font size="4"><strong><em><u>
<a name="3.0">3.0</a> - Chip-8 Instructions
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
The original implementation of the Chip-8 language includes 36 different
instructions, including math, graphics, and flow control functions.<br>
<br>
Super Chip-48 added an additional 10 instructions, for a total of 46.<br>
<br>
All instructions are 2 bytes long and are stored most-significant-byte first.
In memory, the first byte of each instruction should be located at an even
addresses. If a program includes sprite data, it should be padded so any
instructions following it will be properly situated in RAM.<br>
<br>
This document does not yet contain descriptions of the Super Chip-48 instructions.
They are, however, listed below.<br>
<br>
In these listings, the following variables are used:<br>
<br>
<em>nnn</em> or <em>addr</em> - A 12-bit value, the lowest 12 bits of the instruction<br>
<em>n</em> or <em>nibble</em> - A 4-bit value, the lowest 4 bits of the instruction<br>
<em>x</em> - A 4-bit value, the lower 4 bits of the high byte of the instruction<br>
<em>y</em> - A 4-bit value, the upper 4 bits of the low byte of the instruction<br>
<em>kk</em> or <em>byte</em> - An 8-bit value, the lowest 8 bits of the instruction<br>
</font></tt>
<br>
<br>
<font size="3"><strong><em><u>
<a name="3.1">3.1</a> - Standard Chip-8 Instructions
</u></em></strong></font> <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.0">[TOC]</a><br>
<br>
<tt><font size="3">
<strong><a name="0nnn">0<em>nnn</em></a> - SYS <em>addr</em></strong><br>
Jump to a machine code routine at <em>nnn</em>.<br>
<br>
This instruction is only used on the old computers on which Chip-8 was originally implemented. It is ignored by modern interpreters.<br>
<br>
<br>
<strong><a name="00E0">00E0</a> - CLS</strong><br>
Clear the display.<br>
<br>
<br>
<strong><a name="00EE">00EE</a> - RET</strong><br>
Return from a subroutine.<br>
<br>
The interpreter sets the program counter to the address at the top of the
stack, then subtracts 1 from the stack pointer.<br>
<br>
<br>
<strong><a name="1nnn">1<em>nnn</em></a> - JP <em><em>addr</em></em></strong><br>
Jump to location <em>nnn</em>.<br>
<br>
The interpreter sets the program counter to <em>nnn</em>.<br>
<br>
<br>
<strong><a name="2nnn">2<em>nnn</em></a> - CALL <em>addr</em></strong><br>
Call subroutine at <em>nnn</em>.<br>
<br>
The interpreter increments the stack pointer, then puts the current PC on
the top of the stack. The PC is then set to <em>nnn</em>.<br>
<br>
<br>
<strong><a name="3xkk">3<em>xkk</em></a> - SE V<em>x</em>, <em>byte</em></strong><br>
Skip next instruction if V<em>x</em> = <em>kk</em>.<br>
<br>
The interpreter compares register V<em>x</em> to <em>kk</em>, and if they are
equal, increments the program counter by 2.<br>
<br>
<br>
<strong><a name="4xkk">4<em>xkk</em></a> - SNE V<em>x</em>, <em>byte</em></strong><br>
Skip next instruction if V<em>x</em> != <em>kk</em>.<br>
<br>
The interpreter compares register V<em>x</em> to <em>kk</em>, and if they are
not equal, increments the program counter by 2.<br>
<br>
<br>
<strong><a name="5xy0">5<em>xy</em>0</a> - SE V<em>x</em>, V<em>y</em></strong><br>
Skip next instruction if V<em>x</em> = V<em>y</em>.<br>
<br>
The interpreter compares register V<em>x</em> to register V<em>y</em>, and if
they are equal, increments the program counter by 2.<br>
<br>
<br>
<strong><a name="6xkk">6<em>xkk</em></a> - LD V<em>x</em>, <em>byte</em></strong><br>
Set V<em>x</em> = <em>kk</em>.<br>
<br>
The interpreter puts the value <em>kk</em> into register V<em>x</em>.<br>
<br>
<br>
<strong><a name="7xkk">7<em>xkk</em></a> - ADD V<em>x</em>, <em>byte</em></strong><br>
Set V<em>x</em> = V<em>x</em> + <em>kk</em>.<br>
<br>
Adds the value <em>kk</em> to the value of register V<em>x</em>, then stores the result in V<em>x</em>.
<br>
<br>
<strong><a name="8xy0">8<em>xy</em>0</a> - LD V<em>x</em>, V<em>y</em></strong><br>
Set V<em>x</em> = V<em>y</em>.<br>
<br>
Stores the value of register V<em>y</em> in register V<em>x</em>.<br>
<br>
<br>
<strong><a name="8xy1">8<em>xy</em>1</a> - OR V<em>x</em>, V<em>y</em></strong><br>
Set Vx = V<em>x</em> OR V<em>y</em>.<br>
<br>
Performs a bitwise OR on the values of V<em>x</em> and V<em>y</em>, then stores the result in V<em>x</em>. A
bitwise OR compares the corrseponding bits from two values, and if either bit
is 1, then the same bit in the result is also 1. Otherwise, it is 0. <br>
<br>
<br>
<strong><a name="8xy2">8<em>xy</em>2</a> - AND V<em>x</em>, V<em>y</em></strong><br>
Set V<em>x</em> = V<em>x</em> AND V<em>y</em>.<br>
<br>
Performs a bitwise AND on the values of V<em>x</em> and V<em>y</em>, then stores the result in V<em>x</em>. A
bitwise AND compares the corrseponding bits from two values, and if both bits
are 1, then the same bit in the result is also 1. Otherwise, it is 0. <br>
<br>
<br>
<strong><a name="8xy3">8<em>xy</em>3</a> - XOR V<em>x</em>, V<em>y</em></strong><br>
Set V<em>x</em> = V<em>x</em> XOR V<em>y</em>.<br>
<br>
Performs a bitwise exclusive OR on the values of V<em>x</em> and V<em>y</em>, then stores the
result in V<em>x</em>. An exclusive OR compares the corrseponding bits from two values,
and if the bits are not both the same, then the corresponding bit in the result
is set to 1. Otherwise, it is 0. <br>
<br>
<br>
<strong><a name="8xy4">8<em>xy</em>4</a> - ADD V<em>x</em>, V<em>y</em></strong><br>
Set V<em>x</em> = V<em>x</em> + V<em></em>y, set VF = carry.<br>
<br>
The values of V<em>x</em> and V<em>y</em> are added together. If the result is greater than 8 bits
(i.e., > 255,) VF is set to 1, otherwise 0. Only the lowest 8 bits of the result
are kept, and stored in V<em>x</em>.<br>
<br>
<br>
<strong><a name="8xy5">8<em>xy</em>5</a> - SUB V<em>x</em>, V<em>y</em></strong><br>
Set V<em>x</em> = V<em>x</em> - V<em>y</em>, set VF = NOT borrow.<br>
<br>
If V<em>x</em> > V<em>y</em>, then VF is set to 1, otherwise 0. Then V<em>y</em> is subtracted from V<em>x</em>,
and the results stored in V<em>x</em>.<br>
<br>
<br>
<strong><a name="8xy6">8<em>xy</em>6</a> - SHR V<em>x</em> {, V<em>y</em>}</strong><br>
Set V<em>x</em> = V<em>x</em> SHR 1.<br>
<br>
If the least-significant bit of V<em>x</em> is 1, then VF is set to 1, otherwise 0. Then
V<em>x</em> is divided by 2.<br>
<br>
<br>
<strong><a name="8xy7">8<em>xy</em>7</a> - SUBN V<em>x</em>, V<em>y</em></strong><br>
Set V<em>x</em> = V<em>y</em> - V<em>x</em>, set VF = NOT borrow.<br>
<br>
If V<em>y</em> > V<em>x</em>, then VF is set to 1, otherwise 0. Then V<em>x</em> is subtracted from V<em>y</em>,
and the results stored in V<em>x</em>.<br>
<br>
<br>
<strong><a name="8xyE">8<em>xy</em>E</a> - SHL V<em>x</em> {, V<em>y</em>}</strong><br>
Set V<em>x</em> = V<em>x</em> SHL 1.<br>
<br>
If the most-significant bit of Vx is 1, then VF is set to 1, otherwise to 0. Then
V<em>x</em> is multiplied by 2.<br>
<br>
<br>
<strong><a name="9xy0">9<em>xy</em>0</a> - SNE V<em>x</em>, V<em>y</em></strong><br>
Skip next instruction if V<em>x</em> != V<em>y</em>.<br>
<br>
The values of V<em>x</em> and V<em>y</em> are compared, and if they are not equal, the program
counter is increased by 2.<br>
<br>
<br>
<strong><a name="Annn">A<em>nnn</em></a> - LD I, <em>addr</em></strong><br>
Set I = <em>nnn</em>.<br>
<br>
The value of register I is set to <em>nnn</em>.<br>
<br>
<br>
<strong><a name="Bnnn">B<em>nnn</em></a> - JP V0, <em>addr</em></strong><br>
Jump to location <em>nnn</em> + V0.<br>
<br>
The program counter is set to <em>nnn</em> plus the value of V0.<br>
<br>
<br>
<strong><a name="Cxkk">C<em>xkk</em></a> - RND V<em>x</em>, <em>byte</em></strong><br>
Set V<em>x</em> = random <em>byte</em> AND <em>kk</em>.<br>
<br>
The interpreter generates a random number from 0 to 255, which is then ANDed
with the value kk. The results are stored in V<em>x</em>. See instruction <a href="http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#8xy2">8<em>xy</em>2</a>
for more information on AND.<br>
<br>
<br>
<strong><a name="Dxyn">D<em>xyn</em></a> - DRW V<em>x</em>, V<em>y</em>, <em>nibble</em></strong><br>
Display <em>n</em>-byte sprite starting at memory location I at (V<em>x</em>, V<em>y</em>), set VF = collision.<br>
<br>
The interpreter reads <em>n</em> bytes from memory, starting at the address stored in
I. These bytes are then displayed as sprites on screen at coordinates (V<em>x</em>, V<em>y</em>).
Sprites are XORed onto the existing screen. If this causes any pixels to be
erased, VF is set to 1, otherwise it is set to 0. If the sprite is positioned