I will try with MAX 1232 (brown out detector and watchdog).

I have a question about backup supply. I intend to use 7806 voltage regulator with 3.3 ohm series resistor on output. On the output I will connect 4.8V 1.2Ah Ni-MH cell and take power supply for 8051&co from the cell. Resistor is for current limit. Normal power consumption of my project is 0.1 to 0.2 Amps.

Do you think this is ok?

regards, Damjan