Broken calculator

[blackjetrock]

No, the 602 decapping hasn't moved on. I think I need to remove the top layer(s) in order to see the bit patterns and I don't have equipment to do that. I don't want to use acids so may try lapping the die, which will need some equipment to perform.
I have, however, been capturing the ROM contents of a Rockwell 920, using a processor attached to the ROM bus. This sounds similar to what you are trying to do with the Casio (do you mean 805P? or 850?). I am using a Blue Pill and some voltage dividers. I also used a Blue Pill to sniff the display bus on a Casio FX-702P, that is also similar. It was much harder reverse engineering the protocol on that device. There's similar projects and information on this web site:

http://www.pisi.com.pl/piotr433/

Some links to my attempts:

https://www.youtube.com/watch?v=pDH0wQUhD8w&t=16s
https://www.youtube.com/watch?v=PFEQpZJrdY4&t=823s
https://trochilidae.blogspot.com/2020/12...00khz.html

I've also decapped one of the chips in a CQ-1, but that is a whole different story.

Regards
Andrew