Broken calculator

[blackjetrock]

Well, I have to first find the 0s and 1s, I'm not sure I'll be able to do that, but I'm going to have a go once I have a decent clean die shot of the chip as it is at the moment. I've written a tool that should be able to extract the ROM data (I've used it on another calculator, a Casio HL-802, which has it's ROM data visible without any layer removal). Then, it's a case of unscrambling the bits so they are arranged in the correct order. You can use the circuitry that is visible to do some of this, for instance looking at which address lines go to which rows. Then you have to work out what the data is doing. If there's a well known microcontroller then you're OK as you can hopefully get the instruction set. If the ROM drives a custom state machine though, then you'll have to decode that too. It's early days for me at the moment, I'm still coming to grips with what transistor look like and so on.

If you want to see an example of this then have a look at this page, it's fascinating:

http://files.righto.com/calculator/sincl...lator.html