If you use an external oscillator, and divide-by-8 internally, can you apply up to 160MHz on PB6? For example, can I use my 50MHz oscillator to clock my 328p @ 6250KHz? Note: when I say oscillator I don't mean resonator or crystal

1 Answer 1


No! 20 MHz max (Please see 8.8 External Clock, pp. 34). The 50MHz clock could be divided by 8 with a counter or the 150MHz clock by 16 with a faster counter.


  • So divide-by-8 doesn't apply to external oscillators? Dec 20, 2015 at 13:47
  • Exactly. The external clock is max 20 MHz and then it may be divided internally. Dec 20, 2015 at 13:48

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