We have an emission problem with an ATmega324P running with a 16MHz crystal. We get peaks at 32MHz, 48MHz, 64MHz, 80MHz and 96MHz. For some reason the 64MHz and the 96MHz peaks are the highest peaks. They are something like 6dB over the allowed level in the EMC test, the other peaks are well below.
The two layer layout is not very good but the oscillator loop is very small and the oscillator waveform looks good.
This is the first time we have problems of this type so it came as a slight surprise.
Any thoughts on this?