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Micro-KIM Tutorial: The Memory Map

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Let’s revisit the Micro-KIM memory map, introduced in the third tutorial. +-----------+ | 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 +-----------+ Since the default kit (without any expansion) only uses the lower address bits to access 8K, memory repeats itself every 8K. You can verify this by storing and inspecting values in, for instance, addresses $0000 and $2000. Any value stored in one address will show up in the other. Although an interesting factoid, there is no reason to let Micro-KIM programs address anything outside the range $0000-$1fff. Addresses $0000-$13ff contain 5K free RAM (another interesting factoid: the Micro-KIM actually wastes 3K of its 8K RAM chip to keep compatibility with the original KIM-1). This memory region can be used to store da

Micro-KIM Tutorial: Available as Single PDF

If you were following (and hopefully enjoying) the Micro-KIM tutorial, you may have noticed a rather long silence after the last posting. Unfortunately, my day job and a move plus remodeling claimed most of my spare time. However, I plan to continue the tutorial really soon again! In the meanwhile, I have made all previous tutorials available as a single PDF on my Micro-KIM website , where you can also find the source code of all examples. Future tutorials will be added to this PDF to keep the collection available as a single file.

New Chess Graphics for Chess for Android

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Bryan Whitby, who contacted me earlier to tell about very cool USB chess board projects , contacted me recently with a very generous offer to use his awesome chess graphics in Chess for Android . I am very thankful, since these graphics look really good, and combine well with the various board types already supported. So, expect an updated on Android Play and my website really soon! And, thank you Bryan!

Micro-KIM Tutorial: Brightness of LED Display

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A demo is a program that shows off the abilities of a computer or programmer, sometimes even beyond the limits of an original architectural design. For example, a well-known demo theme on the Commodore 64 consists of rendering sprites in the border, i.e. outside the area originally destined for rendering sprites. This tutorial presents demos that use the LED display beyond its (probable) original purpose: adjusting the brightness of characters or even segments. As shown in the previous tutorial, a refreshing loop is necessary to show all 6 characters on the LED display. Here, the refreshing rate directly defines the brightness of these characters. Simply looping around yields maximum brightness, while lowering the refresh rate dims the screen. This idea can also be used to adjust the brightness of parts of the LED screen (characters or even individual segments within the characters). To illustrate this effect, let's modify the program of the previous tutorial (the source

Micro-KIM Tutorial: The LED Display

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The following schematic illustrates what is fun about retro computing: the complete schematic of a microcomputer fits on a single page (a higher resolution PDF can be downloaded from the Briel Computers website). Micro-KIM Schematic. Courtesy Vince Briel - Briel Computers The schematic shows that the 6 character LED display is controlled through some selection logic by the data ports of the 6532 RIOT. Because the 16 pins of the two 8-bit data ports A and B would not have sufficed to control all characters in the LED display simultaneously, instead a few bits of B select one character (value 9 selects the first, value 11 the second, etc.) while the lower 7 bits in A are used to control the 7 segments of that particular character (bit 0 controls the top segment, bit 1 upper right segment, etc.). Note that with this scheme, it is possible to set one character and "go on with the program", as I showed in an earlier tutorial by displaying a very bright 8 in the