Hi

I am using P89C662 microcontroller and must put the controller in power down mode. According to datasheet, the only way to wake the controller is via INT1 or INT2 external interrupts. No other peripherals remain powered I believe.

I manually scan 4x4 keypad on PORT0 in normal operation. I need keypad press to wake up microcontroller. My solution needs to be cheap. What do you recommend?

During power down, could I attach 4-input AND gate to the rows? This would give logic low if any key is pressed? When controller is put into sleep, do the output columns that have been set to zero hold? Or do they become floating?

Any ideas appreciated. Thank you
Javier