RPN scientific calculator firmware for $13 calculator kit

[jklsadf]

These chips are very hard to completely "brick" since the bootloader is permanently burned into ROM, and isn't overwritable as far as I know. Even with no code loaded (or corrupted code loaded) you should be able to start the stcgal programmer software, turn off the calculator by removing the batteries, and then turn on the calculator by reinserting the batteries and pressing the ON button.

The stcgal programmer software continuously sends a special sequence of bytes. On poweron, the STC microcontroller runs the bootloader code (before any other code) to check for this sync sequence, and enters programming mode if found. This should all work even with no code loaded (or corrupted code loaded), since the bootloader is permanently burned into ROM.