Hacking Into The fx-5800p Calculator

fx-5800p Internal Information

1.General Information

SOC: OKI ML610901B (CPU, RAM, Mask ROM, LCD Driver)

Flash: 29LV800CBT (Only half of the Flash ROM is used, weird)

RAM: 62256

Oscillator Type: Unknown, probably embedded.

The oscillation frequency can deviate by a huge amount, probably RC or on-chip oscillator.

2. OS Update

“OS” refers to the binary data residing in the external Flash ROM. In fact, most of the core math, hardware-access, communication, and maintenance functions are hard-wired inside the SOC (Mask-ROM). The font set and the power-off screen are also in the Mask-ROM.

From what I know so far, the UI, statistics, and programming functions are probably in the external flash, which can be reprogrammed.

To enter the OS Update menu:

1. Shutdown the device using [SHIFT]+[AC/ON]

2. Hold [MODE]+[7], Press [AC/ON]

3. Press [⬅️], then [9]

You’re now in the maintenance menu, press [2] for OS Update functions. (Warning: you may accidentally delete your OS, be careful. Self-test or OS Update will cause a memory clear)

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