The Sharp MZ-40K 'Micro Computer Doctor' is an electronics computer-like kit designed for children and released in May 1978 in Japan and it would appear the first Sharp 'computer' product to use the ‘MZ’ name. There were a few add-ons that could be purchased separately and at least one planned expansion that was advertised but never available.
Because you couldn't program the MZ-40K in much of a meaningful way- you could enter musical notes but not use a programming language - the MZ-40K was more of a toy than a computer, yet it no doubt served as an introduction to electronics and computing in a somewhat affordable manner.
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When originally released the MZ-40K sold for ¥24,800 or, if we adjust for inflation, in 2025 is ¥42,464.05 or £216.67/$292.94.
If we look in the September 1978 issue of the Japanese computer magazine I/O:
https://archive.org/details/io-197809
On page 42 (publication page number) the MZ-40K is advertised selling for ¥24,800 but I couldn't find the MZ-40K for sale in later I/O issues.
The heading translates via Google Translate as 'Sharp microcomputer kit', for the accompanying text I used DeepL Translator as it did a better job than Google:
Clock, timer, phone charges
Money display, automatic music, various games
keyboard playing
The 'automatic music' likely means the playback of programmed in music.
Additionally there is text reading:
*Sold separately
Sensor Kit
¥2,950
So that means we have a price for the sensor kit (at least for September 1978), if we adjust for inflation, in 2025 is ¥5,051.17 or £25.77/$34.85.
It would appear that the MZ-40K was at least also sold in Germany (or other German speaking country) in addition to Japan, since there is an online copy of the MZ-40K manual in German, but further details, such as release date and cost, are unknown.
The German MZ-40K manual and other related documents can be found at:
https://archive.org/details/sharp-mz-40k-handbuch/Sharp%20MZ-40k%20Handbuch/
The additional documents are the (translated from German) 'car racing' and 'big game hunting' game sheets, and 'MZ-40K Usage Chart'.
The MZ-40K can be split into four main parts; input (hexadecimal keypad, as well as optional sensor inputs and organ keyboard), memory (ROM and RAM), CPU ( X0036PAZZ), and output (speaker and 7-segment LED display). The CPU, as Sharp calls it, is actually a 4-bit microcontroller based on the Fujitsu MB8843 which features 1K x 8-bit mask ROM, 64 x 4-bit static RAM (SRAM), 4-bit CPU, and 32 general purpose I/O, as well as serial and interrupt support. Additionally, the MZ-40K circuit uses two X0043PAZZ ICs, equivalent to 8101/2101, which are 256 x 4-bit SRAM chips.
You can find the datasheets for the various chips used in the MZ-40K at:
https://www.sharpmz.org/mz-40/dldsh40k.htm
As featured in the same I/O magazine previously linked, there were, for example, the much more sophisticated computer kit NEC TK-80 selling for ¥88,500 and the NEC TK-80E for ¥67,000, which could be seen as rival kits.
The TK-80 was released in 1976, you can view some info and photos at:
https://museum.ipsj.or.jp/en/computer/personal/0002.html
Notice that there are some similarities to the MZ-40K, although you could say they were necessities; the 7-segment displays (two groups of four contrasts with the MZ-40K's one lot of four), and the hex keypad (5 x 5 keys although MZ-40K only has the digits in the same positions and has three less keys).
While the MZ-40K could be seen as Sharp 'testing the waters' with a computer-like product without committing to a fully fledged computer kit, they released the MZ-80K in Japan in the same year, a 'proper' programmable computer with of course a much larger price tag.
The MZ-40K is rare to come across nowadays, I don't have any figures of how many of the kits were made, how many were sold, and which countries it was available in although it would appear at least Japan and Germany. I have seen as of 2025 several MZ-40Ks on eBay, some in their unused form, others assembled, selling from Japan for ~£380/$508.88 and above, which at least means we have some high resolution images of the kits. The few sites that have documented in detail the MZ-40K are from a time ago and the images are of lower quality, nonetheless the information of those sites is very useful.
Despite the limitations of the kit (that is, it isn't a computer as such) I do believe it makes for a worthwhile kit to appreciate Sharp's original endeavour, as a learning tool, and a bit of nostalgia too for a time of old. To be clear, the goal of recreating the original kit initially is to get the main circuit working and usable as if it were the real kit, and so it resembles the original kit as much as is possible. Making a similar case for it would be the next goal and as the MZ-40K did have two add-on modules but that would be covered far in the future.
While the MZ-40K uses mostly off the shelf components there is one particular piece that is the biggest hindrance to recreating the MZ-40K, the Sharp X0036PAZZ, which Sharp referred to as the 'CPU' even though more accurately it's a microcontroller, containing a CPU, RAM, ROM and I/O interfaces, based on the Fujitsu MB8843 4-bit microcomputer from 1978, the datasheet can be found at:
https://datasheets.chipdb.org/Fujitsu/MB8840.pdf
The MB8843 is a very capable chip and so it's not surprising that it was used in a number of products, from Namco custom chips in arcade machines to controllers in cassette decks from Sony and Akai to give a few examples.
Although the MB8843 can as of 2025 be bought from eBay from various countries at a not too ridiculous price the real problem is they contain a 1K x8 mask ROM (the data is set at the time of manufacture). I did try looking for X0036PAZZ on eBay but there were no results and Googling X0036PAZZ only returned one result.
The 1K in the MZ-40K's microcontroller presumably contains the firmware for the kit (note that the instruction opcodes are 8-bit, which may be why it's an 8-bit ROM rather than 4-bit) and some option settings also contained in the mask ROM, none of which can easily be obtained. The MB8843 ICs I found on eBay are likely taken from or are spares from various products, so the ROM will have already be programmed.
As the X0036PAZZ isn't readily available but is essentially a MB8843 it would have to be emulated and the firmware written from scratch to match the features of the original kit, so an Arduino or similar board could be used for flexibility when testing, eventually replaced with a CPLD (Complex Programmable Logic Device) as a drop-in replacement. As mentioned, without the original firmware the only option is to write the code using the information from the kit manual to recreate the features which of course won't result in an exact replica.
As mentioned, the MB8843 was used in a number of arcade machines as mentioned here:
https://en.wikichip.org/wiki/fujitsu/mb8840
"The MB8840/MB8840H series is a family of 4-bit nMOS microcontrollers... This series was very popular for arcade games (e.g. some Atari's Namco Galaga/Xevious systems)."
On this site:
https://pixelatedarcade.com/tech_attributes/overview/fujitsu-mb8843-1-536-mhz
It says that three games use the MB8843; Galaga, Pole Position, and Pole Position II, which we can confirm by checking these links:
https://pixelatedarcade.com/games/galaga/techspecs
https://pixelatedarcade.com/games/pole-position/techspecs
https://pixelatedarcade.com/games/pole-position-ii/techspecs
I also came across:
https://github.com/opengateware/arcade-xevious
Which is a "Namco Xevious Compatible Gateware IP Core". On the page we can see:
"Sound Chip: Fujitsu MB8842, MB8843 and MB8844 @ 1.536 MHz"
If we go to:
https://github.com/opengateware/arcade-xevious/tree/master/modules/cpu-mb88xx
We can see the files index.qip and mb88.vhd, which look to be for a CPLD/FPGA, so we could possibly use those files to implement a MB8843 in CPLD/FPGA. However, having looked through the files I can see that currently some features haven't been implemented although the code is still very useful.
I also looked at the MAME emulator:
https://github.com/mamedev/mame
It also covers the MB88xx series:
https://github.com/mamedev/mame/tree/master/src/devices/cpu/mb88xx
The mb88dasm files are for a Fujitsu MB88xx series MCU disassembler.
The mb88xx files are for the Fujitsu MB88xx series MCU emulator. Looking at the .cpp file we see they define the device type (MB8843 is an option), and a couple of guesses have been made for some constants. At the time of checking, not everything has been programmed, and would require heavy modification to run on an Arduino but nonetheless would be very helpful.
What I decided was to emulate the MB8843 on an Arduino Mega (since that has enough I/O), because of time constraints I tried using ChatGPT to generate a base Arduino sketch from the MB8843 datasheet, it did manage to write some code to get me going, which I've heavily modified since. Since I couldn't find a MB88xx series assembler for download I had ChatGPT write one in Python and added to it, once it's complete I'll add it here for anyone to use.
This is of course an ongoing project but if anyone has any information about the MZ-40K that could be useful for this project then please contact me at james.boshikoopa@gmail.com.
More to be added soon...
All content of this and related pages is copyright (c) James S. 2025