~Let's make 30-year-old pocket organiser Casio Business Navigator BN-20 run some new software, part 4~
Recap of the previous episodes: our friend gave us a pocket organiser. As it happens, the organiser is based on Intel 8086-compatible core. It is related to Casio Pocket Viewer series, but unlike the PV, it doesn't have a way to "side-load" the applications.
So far we've dumped the ROM and tried to use it with Casio PV SDK. PV is compatible enough to kick-start the boot process, but the simulated OS crashes before it can even draw anything.
One interesting lead I decided to follow was the discrepancy between the CPU models in BN-20 and PV series: BN-20 runs on NC3020, and PV runs on NC3022. The documentation for Casio PV SDK mentions that a publicly-available simulator for NC3020 was a thing, too.
Can we find it? Can we run it? Yes we can!
🧵
As some of you might guess, back in the 90s Casio had completely different PIM series for its internal (Japanese) and external markets. It made sense to focus on hand-written text recognition for the Japanese input, and it didn't make all that much sense for English/French/German/Italian/Portuguese/Spanish, where QWERTY/AZERTY/QWERTZ was clearly superior. So, you won't find Business Navigator on the Casio's Japanese website. But you can find something called "Casio Caleid Multimedia Navigator". Look closely, don't you think some of the icons are the same as on our BN-20?
(The photo comes from Yahoo Auctions)
A blog featured by @osnews@mstdn.social in https://www.osnews.com/story/136806/casio-caleid-xm-700-mobile-navigator-1997/ claims that there used to be an SDK for it. Is it still up online somewhere? Is THAT the mythical SIM3020 mentioned in the SIM3022 documentation? Spoiler: yes!~
(cont)
Following the link trail, I arrived at two interesting destinations. One is a website about making Add-Ins for Caleid, and another is Casio's own website, offering a tool for making Add-Ins. The Caleid portal had one and only file preserved by the Internet Archive (bravo!), a 2.2 megabyte LZH archive with a Setup for the Add-In maker.
First, I discovered that the Setup program requires Windows 95 (luckily, I still have my Windows 95 hard disk image). Then I discovered that the Setup program requires a Japanese Windows 95 - otherwise it crashes.
I was hoping to unpack the InstallShield Z archives with "unshield" tools, but the ones I've found did not handle CP-932 correctly and failed to unpack the installer. Can't be helped, time to get my PC-9821 laptop unpacked!
...turns out, it was the right call: the emulator requires PC-98.
(cont)
Installer finished its job, and it became clear that the Casio Caleid SDK is likely one of the missing pieces I need to reverse-engineer my BN-20 organiser.
The Caleid SDK comes with SIM3020, the simulator for the exact CPU model used in the BN-20. This is significant, because NC3020 and NC3022 have 4KB of a built-in firmware that must be different between the chips and probably contributes to incompatibilities.
SIM3020 is also significantly simpler. It doesn't have an MDI interface, or a complex ROM/RAM/Flash configurator. It isn't even a Windows program; it is a DOS program for a PC-98 series computer (that might work on DOS/V under Windows 95, according to the docs, but I couldn't make it).
Fun: despite being shipped as a device simulator for touchscreen-based XM-700, it also simulates a hardware keyboard.
(cont)
If SIM3020 is a DOS program, it should run under DosBox-X in PC-98 mode, right?
I switched my DosBox-X to PC-98 mode, thought hard and long about the program's complaints about EMS and XMS, and eventually came up with a DosBox configuration file that allowed the simulator to start. That's very neat.
(Protip: >16MB of RAM, both EMS and XMS, required; EMB is another name for XMS)
Time to look what's inside...
(cont)
Casio PVOS SDK ships with the OS in a single file, called BIOS. Caleid SDK comes chunked into multiple segments, each under 64KB (totally normal thing for an x86 embedded device, I suppose).
CPU.00/01 have the initial BIOS/bootloader; I haven't diff'ed it with the code from NC3022, but I suppose it is going to be somewhat different. There's very little code in it, though.
Then there's LIBINT; probably library for internalisation. Could it be a file that is different between Japanese and Western models? It has huge tasty bitmaps of numbers and days of week.
(cont)
CALEID.00 is the main entry point for the Caleid OS. Despite being merely 14 KB in size, it stores a ginormous bitmap with the icon placeholders (taking 7 kB out of those 14).
Caleid.01 and .02 system files do not seem to feature anything interesting bitmap-wise at all, which is a major difference from how things are done on Casio BN-20 (that one was full of bitmaps). The Caleid SDK doesn't seem to ship with Caleid built-in software, either; there's no memo or spreadsheet in the OS files.
However, Caleid.03 and Caleid.04 system files hint that there is something called "LCD BIOS" and then there is a tool that asks the user to draw a kanji! Could it be that there's hand-written recognition tooling? In <256 KB of code? 🤔
I'm also extremely curious whether Caleid had a kanji font bank. I guess I might find out soon enough.
(cont)
The sysbin/data folder has multiple files CALEDATA.xx. Files 01-18 are font files. There are 8-pixel wide extended ASCII fonts (including symbols for musical notations - Casio is a musical instrument company!), 8 pixel-wide kanji, 1 pixel-wide kanji and 24 pixel-wide kanji. Some of the fonts are very pretty.
(cont)
I assumed that Caleid SDK didn't ship the full OS - because the SIM3020 immediately boots into the Add-In program - but it seems I am wrong. CALEDATA.20 file has the launcher, coming with the full-sized bitmaps. So pretty T_T
There are place-holders for the pop-up windows, too. What a curious little operating system.
(cont)
The contrast correction UI is something we've seen already, in both Casio BN and Casio PV, but this list of on-screen keyboards (including handwriting recognition keyboard) is something I personally have not seen before in this product series.
(cont)
What is the most optimal way to make a monthly calendar program? Why, of course pre-render the calendar and store it is a bitmap in the ROM.
How ELSE are you going to use all this massive 2 megabyte ROM?
This operating system is something else.
(cont)
CALEDATA.30 stores a different part of the Casio Caleid OS - the applications. It also features the very same images we've seen in our BN-20 BIOS. I'm uploading them here upscaled and colour-corrected.
The "notes" application has lots of different categories of notes: cars, cards, CDs, books, films, and so on.
(cont)
Some more built-in apps in the Caleid OS: "easy sheet" is a spreadsheet program with built-in templates (mortgage, currency converter, GOLF SCORE wtf) and the networking app (computer, electronic mail, FAX).
(cont)
What could be better than a calculator app? Well, of course, two calculator apps! Yes, Caleid has two built-in calculators: one is stand-alone and one is a pop-up calculator. Handy, eh?!
(cont)
Caleid is a "Mobile Navigator", not a "Business navigator", so it has three built-in games.
The last file in the OS, the 300 KB blob CALEDATA.40, doesn't have any non-compressed bitmaps.
Can we run the OS in the simulator? It is shipped with it, after all. Hmm... Let's try! (cont)
Well, actually, I can't think of a way to do so... Maybe some other time.
Anyhow, I've uploaded the Caleid OS and the SIM3020 to the Internet Archive: https://archive.org/details/caladdin/Screenshot%202026-02-01%20at%2015.16.33.png
Grab a DosBox-X with PC-98 support and try it yourself~
Nina Kalinina