After any Reset, CLK_MAIN is provided by the
16/20MHz oscillator (OSC20M) and with a Prescaler
division factor of 6. Since the actual frequency of the OSC20M is determined by the Frequency
Select bits (FREQSEL) of the Oscillator Configuration fuse (FUSE.OSCCFG), these frequencies
are possible after Reset:
Table 1. Peripheral Clock Frequencies after
Reset|
CLK_MAIN
as per FREQSEL in FUSE.OSCCFG
|
Resulting CLK_PER |
|---|
| 16MHz |
2.66MHz |
| 20MHz |
3.33MHz |
See the OSC20M description for further details.