8.10.2 Starting-up of Crystals

The characteristics of power-up crystals are as follows:

The power-up of the SoC happens with the internal oscillators.
After the power-up, the boot ROM code will either run on internal FRC oscillator only or turn on POSC+PLL and switch to 128 MHz, depending on seccfg[1:0]. After execution of boot ROM code, the user software can request to switch on the SOSC and the POSC crystals, if necessary.

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