When using an external oscillator as the 26MHz source, we can not adjust the amplitude to the desired range based on section 22.214.171.124 Adjusting the 26 MHz Oscillator Trim of the reference manual. I have tried reducing the drive voltage from the oscillator but it did not help. the OSC26M_AGC[5:0] register is 0 and the OSC26M_PEAK[1:0] says I need to trim lower.
We do not have this problem when using a 26MHz crystal.
When using the external oscillator, we can not properly shutdown the MPLL to go to low power sleep.
Could the sleep problem with the external oscillator have anything to do with the trim adjustment problem?