Aart's Blog

A simplified memory map of the Micro-KIM is shown below. This tutorial explores the 2K EPROM,  leaving a more detailed exploration of the free RAM and 6532 RIOT for later.  Address space $1400   to   $173f  is unused i n the standard Micro-KIM kit configuration.    +-----------+   | 2K EPROM   |$1fff   | monitor   |   | program   |$1800   +-----------+   | 6532 RIOT |$17ff   | I/O, timer|   | and RAM   |$1740   +-----------+   | optional  |$173f   | I/O, timer|   | and RAM   |$1400   +-----------+   |           |$13ff   |  5K RAM   |   |           | $0000   +-----------+ Addresses  $1800 through  $1fff  are taken by the 2K EPROM, which is a read-only memory area that stores the 6530-003 and 6530-002 parts of the...

At the lowest level, the 6502 executes numerical machine code. For example, the following bytes in hexadecimal format constitute a simple program that displays a single 8 on the LED display of the Micro-KIM.   a9 ff 8d 40 17 a9 09 8d 42 17 4c 0a 02 Let's enter this program into the memory of the Micro-KIM. Power on the kit with jumper JP2 off and press the RS key. Then enter 0200 to set the address and press DA to go into data mode. Next, enter the numbers above pressing the + key after each number pair (so, enter A9 + FF + etc.). Before running, I strongly recommend checking the values. Use AD to go back into address mode. Press 0200 again and use + repeatedly to check all entered values. Once satisfied, press 0200 and GO. If all goes well, you will see a very bright 8 as first digit on the LED display (in later tutorials I will explain why). Displaying a single digit on the Micro-KIM Obviously constructing and entering programs this way is tedious and er...

Perhaps reminiscing the past is a sign of getting older, but I cannot help but look back fondly at the times I learned programming machine code on the Commodore 64 in the eighties. Therefore, it is probably no surprise I still occasionally enjoy programming 6502 on the Micro-KIM, which is a modern replica of the seventies KIM1 microcomputer, made available by the well-known retro computer kits provider  Briel Computers . In fact, I am having so much fun with this board, I decided to write a series of tutorials on operating and programming the Micro-KIM. In this series, I assume you have already some experience with the Micro-KIM and 6502 machine code, and have read the basic documentation that is shipped with the kit. Other than that, I hope to give additional information on various topics, such as developing assembly programs, programming the display, using the RS232 port or keypad, setting up timer-based interrupts, using a cross-assembler to generate programs in paper tap...

A rainy weekend was a perfect excuse to play with my micro-KIM, which had been collecting dust in a drawer for too long. I had fun using my own cross-assembler to develop and generate programs in paper tape format, and upload these to the micro-KIM via the PuTTY client. I figured out how to use the 6532 RIOT to set up a timer-based interrupt service, which is an important step in separating actual computation from display and keypad handling. The following clip shows the difference between incrementing a three-byte memory counter at roughly 1000 times per second (timer delayed) and 100,000 times per second (full speed with about 10 cycles per iteration at 1MHz). Perhaps a nice illustration of how fast even those early computers were.

Not everyone was happy with the "swipe-up" to open the options menus (for devices that lack a menu button, or that broke the legacy options menu altogether), so I decided to simply implement an on-screen button instead. I also improved the graphics in the on-screen buttons for navigation, something that as long overdue. The result is shown below. The right-most button with the horizontal lines opens the new-style options menu. As before, the other buttons are used for navigating the game, see the manual for details. On devices that still support a physical or virtual menu button (vertical dots in the screen-shot below), that button opens the legacy options menu. Expect a similar update for Reversi and Checkers for Android soon too.

A while back I got an email from Isaiah James D. Puzon, a computer engineering student at the Philippines FEU Institute of Technology, with a minor request for a new feature in Chess for Android that would help with his thesis project: a chess-playing robotic arm. It was very rewarding to receive pictures from his exciting working prototype a few months later. You did a great job building this robot arm, Isaiah. Congrats with your graduation and good luck with your further career!

I got several questions on how to use the opening book features in Chess for Android , so I hope this blog posting will be useful. By default, the GUI uses a built-in opening book before it consults any chess engine, either the built-in Java engine, or an imported third-party chess engine. This small built-in opening book (consisting of few opening lines I studied a long time ago as a young member of a chess club, by the way) provides some variety of play, but otherwise is probably not sufficient for the more serious chess player. Therefore, before using an engine's own opening book, one has to disable the GUI opening book, by disabling the "Use Book" choice in the options menu, as shown below (touch to remove the check mark). It may seem a bit counter-intuitive to disable the "Use Book" feature in order to use an engine's opening book, but without doing this, the GUI will first consult the built-in opening book before consulting the engine, so...

I have also improved the graphics and animation in Checkers for Android. You can see the result in the video below. Both the reversi and checkers updates are now available on Google Play .

Reversi for Android is getting a graphics overhaul! The "retro stones" have been replaced by stones with a gradient. A new animation on placing and flipping stones makes it more clear what moves just have been played. Except an update on Google Play soon!

I just released new versions of my Android applications, as usual available on Google Play or as direct download . These versions introduce a new options menu dialog that can be accessed by swiping up. Hopefully this provides a viable alternative on devices that lack or broke the legacy options menu button. Reversi for Android v2.5.5 Checkers for Android v2.6.5 Chess for Android v5.1.5 Chess for Android also introduces a slightly cleaner position set up window, and added the ability to define an opening book for an imported UCI or XBoard engine. Please let me know if all works well.