[sdiy] NEC D936CT chip in my Muppet Babies keyboard

dh at atoav.com dh at atoav.com
Sun Jul 9 22:57:29 CEST 2023


If you really cannot find the pinout (and/or nobody here can help) I 
would examine the environment of the chip on the board very carefully, 
probably even try to reverse-engineer it into a circuit diagram. The 
power pins could be identified very easily that way.

I would also probe the live circuit with the chip still in it, possibly 
by soldering thin wires to the legs of the IC. That way you can try to 
find fixed DC voltages (Vcc) very easily, the rest can be guessed by 
correlation (e.g. if something has DC but goes low when you press a 
button, that might be the input for that button and it also tells you 
which voltage is used and whether you have to pull it up or down).

Of course the easier way is to find a datasheet, but if this is a custom 
chip (and it sounds like it) you probably won't find any as it is not a 
commercially sold IC.

Best,

David

On 09/07/2023 20:51, Benjamin Tremblay via Synth-diy wrote:
> I cannot find any pinouts for this chip.
> I pulled if off the board (very carefully for me). Now I am trying to guess which io pins scanned the keys and switches.
> I can’t find a pinout for this chip anywhere. Octopart denies its existence.
> Not the same chip as the Casio VL and PT series monophonic keyboards, but hopefully somebody got a bonus for cramming the VL-10 functionality into this 28 pin DIP.
> 
> Ben
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