The Science Fair Microcomputer Trainer is a great learning tool, but I’ve always felt the manual made it difficult to quickly (re)acquaint yourself with the instruction set. This seems particularly important with the the type of sporadic put-down/pick-up use that you might expect with any learning platform, especially one aimed at youngsters.

Unlike the Gakken FX R-165, on which it is based, the Science Fair version lacks a quick reference card (available at the end of the Japanese manual scan). Sure, the Microcomputer Trainer has the opcodes listed on the front panel, but it's not quite the same. So, please, allow me to present: The Missing Manual [Pages].

You can download your own copy here.

Some time ago I put together my own Command Quick Reference for the Science Fair. It’s not a direct translation of the Japanese, as I added a few extra hints to it (e.g. listing the run mode and games) and corrected a couple of minor errors from the original documentation; but it is clearly heavily inspired by it.

As you can see, I keep a printed copy with the unit for reference. If you print it at 85% and trim it with ~5mm margin (to the content) it neatly matches the dimension of the manual. I also find it useful as a cross reference back to the official instruction definitions in the Science Fair Microcomputer Trainer manual (as with the Japanese version, the page numbers refer to the callout boxes).

Some time later I discovered further details about the R-165's E3 CAL INPT instruction. Unfortunately the relevant pages were missing from the Japanese manual scan, but a fellow going by the name mikecat_mixc put up an interesting article on the R-165 which (with the use of Google Translate) allowed me to expand my documentation.

I subsequently added the included “Appendix B” to cover the use of the E3 CAL INPT instruction with the Science Fair, which, even though it is marked as NOT USED, is present and works just fine. Without access to the the Japanese manual this section of the document was much more speculative. You'll have to forgive my potentially poor explanations and examples!

In addition, although it was great to be able to use the "hidden" input feature, the transistor inverter approach seemed suboptimal. Using the "official" circuit means that you can’t use the keyboard and CAL INPT at the same time. However, I realised the limited number of patterns displayed on the seven segment display allowed us to abuse the “HEX. LED” as the input for a simple diode OR gate from which to supply the activation logic and power for the K inputs.

The diode approach actually ensures the display is on during CAL INPT. More importantly, it allows you to use both the keyboard and the CAL INPT command “simultaneously”. I present both options in the document. We have since discovered that the requirement of the display being “on” is just an artefact of the logic used to read the control keys, and the way the output PLA is used (in part) to scan the K inputs.

More recently I obtained the “missing” pages from the Japanese scan (and English translations), and my Appendix B and example program is very different from the originals. There are some possible minor misrepresentations, as this document predates our latest investigations, but I’m happy enough with it. Importantly, I think a diode logic approach, offering access to all four K inputs, is an improvement due to the enhanced functionality it offers.