The ATMEGA256RFR2 Xplained Pro kit contains two crystals that can
be used as clock sources for the ATmega256RFR2 device. Each crystal has a cut-strap next to
it that can be used to measure the oscillator allowance. This is done by cutting the strap
and adding a resistor across the strap. More information about oscillator allowance and
safety factor can be found in appnote AVR4100.
Table 4-8. External 32.768kHz
Crystals| Pin on ATmega256RFR2 | Function |
|---|
| PG3 | TOSC2, crystal output |
| PG4 | TOSC1, crystal input |
Table 4-9. External 16MHz
Crystals| Pin on ATmega256RFR2 | Function |
|---|
| XTAL1 | Crystal input |
| XTAL2 | Crystal output |
