Home Page Forums MAME MAME Request: Casio SA-series keyboards

A decade ago I bought on eBay a big box of Casio service manuals (mainly 4-bit/squarewave era and Super Drums stuff) but have no intact scanner.

Around 2000 also W.D. Greenhill used to sell Casio service manual copies (likely only as PDF) but at that time I refused to throw money into the throats of that doubtful business. Now their Casio stuff is likely all gone (nothing mentioned on their website). I remember they had e.g. those of Symphonytron 8000, Casiotone 201, 202 and VL-5 those I never saw anywhere offered again.

https://www.wdgreenhill.co.uk/contact

Just to bring things back to the original topic, here's a close-up of the off-the-shelf Holtek HT37B90 MCU from the SA-46 (first released 2010, still sold today).

Mine has an embossed datestamp of 2019-2020, so definitely not the original production run, but they probably all use the same MCU. As far as I can tell, the SA-65/66 (and SA-75?) from 2001 were the last to use the MSM6387.

Sams Technical Publishing has a lot of photocopied service manuals available, including all the ones you mentioned and dozens of other pre-CTK models. The downside is that they're each $25 USD for hard copies, and I have no idea how good the quality is.

So that one is Holtek too. I own a Casio SA-76 with similar CPU.

CPU = "HT37B90, CCTECH CD-1, 94V-0 [9 .6 ], MX818-MA4M A" (36 pin COB)

The COB module layout itself differs, so the external pin names are in different places.

Interesting is that of SA-46 and SA-76 exist each in a 2nd version (SA-47,SA-77?) which AFAIK only differs in the sound of the separate "piano/organ" button (has "piano/harmonium" for the India market?).


I finally ordered a 4-channel digital oscilloscope (Siglent SDS1104X-E, in unhacked state 100MHz) before the euro becomes worthless. Will this be a sufficient tool to analyze 1980th/90th keyboard soundchips?

(I also got a 16 channel logic analyzer module for my laptop. Let's hope that the now coming nuclear war won't fry everything of semiconducors by the high altitude EMP nor incinerate me together with the city.)

Nice of them to label all of the MCU's pins. I assume this is ARM based?

The architecture is Holtek's own 8-bit thing; the datasheet has more info. There are also a bunch more (unused) I/O pins that aren't exposed by that little breakout board. The ROM is still all internal, naturally.

Alesis Harmony 32 - Full Review:

The thing was also released as "Alesis Melody 32". In this video at 3:54 the chip is labelled "SunnyWay, ARK-88, 20201105", which may be another Holtek MCU.

http://www.sunnywaytech.cn/cs-genpur.html

This keyboard functions ok, has USB midi, but everything is very mediocre. E.g. all held notes slowly decay, which I last time saw in Casio MT-30 or such.

If anybody wants some spare MSM6387s to mess around with, I bought four of them from this eBay listing and they all work. The program number (31) is from the SA-41, which is the Indian localized SA-21, so you can just swap this into any of the models that have MSM6387-11 to get the different demo tunes. (I don't actually own one, so I just whacked something together on a breadboard instead.)

I'll be experimenting with the test pins at some point soon-ish.

Dtech told me that he had decapped the SA-series CPU long ago and tried to decipher the rom contents (dumped as analogue voltages through the DAC output?), but couldn't figure out how the sound hardware (which is actually a softsynth) works.

How did he manage to do that? Is any of this actually available somewhere?