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 Forum index » DIY Hardware and Software » Microcontrollers and Programmable Logic
Mostek MK3870: how to extract firmware? (Bontempi Eclipse)
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CYBERYOGI =CO=Windler



Joined: Aug 05, 2012
Posts: 10
Location: Germany

PostPosted: Sun Aug 05, 2012 8:51 pm    Post subject:  Mostek MK3870: how to extract firmware? (Bontempi Eclipse) Reply with quote  Mark this post and the followings unread

I have bought an eprommer "Willem Pro4 isp" (had to fix several transistors and make own adapters) and started to dump the EPROMs, ROMs and other readable ICs of my huge music keyboard collection (possibly to start an emulator project like MAME).

Did you know that e.g. early Casio keyboards had a CPU compatible with Intel 8049? Unfortunately the "Willem Pro4 isp" eprommer had a way too weak power supply with tiny SMD transistors switching the voltages. One was burnt anyway, so I had to install bigger non-SMD ones to get the MCS-48 adapter to work. Casio "D8049C xxx" ICs need Vcc of at least 4.5V to read properly, which was impossible with the original transistors ans PSU (it gave only 4V even in 5.6V mode). I installed a 10kOhm resistor into the EA line to avoid damage by the +12V if the IC would not have supported it properly, and connected it to a 5kOhm potentiometer to vary the voltage, which I didn't need. (Too high EA voltage (15V) outputs only "00" while too low voltage (9V?) makes the CPU run its program and output garbage. At too low Vcc it repeats the first part of the rom again and again.) So I e.g. could read the firmware of the Symphonytron Casio CT-8000 cpu and Casio HT-6000 synth (its D80C48 seems to be a real CMOS IC that draws less current). Also MT-36,MT-40,MT-90/MT-200 and Casiotone 401 have such a CPU.

- Is it possible to dump the ROM of a Mostek MK3870?

In my Bontempi Eclipse (bizarre analogue keyboard with programmable rhythm) I discovered this Microcontroller (even socketed):

MOSTEK (c)
MK3870/42
MK1618N-IRL
B-27430580
(upright) 8225

It would be interesting to examine the accompaniment patterns etc. and possibly hack or emulate it. Is it possible to extract the rom contents from the Mostek MK3870, e.g. by applying a voltage to the TEST pin and using other pins as address/data lines?

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