I'm about to connect an external 32kHz digital clock signal (not a 32kHz crystal) to TOSC1 for using Timer2 in Power Down mode. The data sheet for ATmega16 states this about the T/C2 async:
The Oscillator is optimized for use with a 32.768 kHz watch crystal. Applying an external
clock to the TOSC1 pin may result in incorrect Timer/Counter2 operation. The CPU main
clock frequency must be more than four times the Oscillator frequency.
Is that quote saying that connecting anything else than a crystal may result in incorrect operation, or is it stating that connecting anything else than 32kHz (crystal or other) may result in incorrect operation, or is it anything else than a just a 32 kHz crystal that may cause incorrect operation?
The last two sentences is indicating that it is the frequency that is the focus.