Casio fx-5800p recovery

In rare cases, the firmware of the FX-5800P may be corrupted. After booting, the screen displays:

ROM!!!!!
At this point you should try to remove the battery and leave it for 1 hour, then replace the battery and turn it on again. If the problem is still not resolved, you need to use another working FX-5800P for firmware recovery. First, you need to use a 3pin data cable to connect the working FX-5800P to the faulty FX-5800P. Then proceed as follows:

On the normal FX-5800P
First press simultaneouslyAC/ON,MODEwith{\displaystyle 7}7Three keys. The screen displays "DIAGNOSTIC MODE, Factory use only". Press now←And then press{\displaystyle 9}9.
Note: All data in the calculator will be cleared.
Press{\displaystyle 2}2, select "OS UP Send". (sending system)
On the faulty FX-5800P
PressFILEThen select "OS UP Recv". (receiving system)
After the transmission is completed, the faulty FX-5800P can be restored.

Note: Do not reverse the sender and receiver, otherwise the FX-5800P will be damaged.