Hi,
Which part for internal OSC you want to know? I suppose you are referring to the main oscillator instead of RTC OSC, right?
For the main oscillator, there are different oscillator modes, low frequency, high gain, low power, etc. And you can configure the exact mode used with MCG_C2 register.
For the different mode, the external circuit connection is also different, please refer to OSC chapter for detailed information.
Hao