MB90Fxxx

Baudrate select: 
osc  4 MHz - Baudrate  4800
0sc  8 MHz - Baudrate  9600
osc 16 MHz - Baudrate 19200


The 01h data programmed at Flash Security Controller address (FF0001h) 
activate security feature. Any other data leave chip unsecured. 
If the flash security bit is set, it is not possible to program or erase Flash!