The maximum clock frequency that can be used with the internal oscillator is 72 MHz.
To configure the pin multiplexing for I2S, set the PINSEL0 register to select the I2S function for the desired pins (e.g. P0.0 for I2S_WS, P0.1 for I2S_CK, and P0.2 for I2S_SD).
The minimum voltage required for the ADC to operate correctly is 2.4V.
To enable the BOD feature, set the PCONP register to enable the BOD, and then set the BODVOLTAGE register to the desired voltage threshold.
The maximum current that can be sourced or sunk by a GPIO pin is 4mA.