Forum TI-Planet.org

Hi,

I´m trying to downgrade a CASIO Prizm calculator but I can´t seem to find an answer for it. I saw somewhere that by pressing the F2-4-AC/ON and Restart once the calculator was turned off, I would be prompt to a black screen so I then I would press 9 and install the OS. But nothing happens. Currently the calculator is in version 3.1.02

Thank you in advance

Hi.

You just need to put the calculator in "OS error" mode using the F2-4-AC combo, and it'll then accept any OS version.

The combo is just very tricky :

• press and hold the restart button on the back
• without releasing it, press and hold the

  F2

  4

  AC

  keys
• without releasing these 3 keys, release the restart button
• now only release the

  F2

  4

  keys together
• wait a second
• now finally release the

  AC

  key
• press and hold the

  9

  key
• wait a second
• release the

  9

  key
• press and hold the

  ×

  key
  You should now get the OS ERROR screen.
• release the

  ×

  key

It worked. Thank You. I didn´t have the correct key combination