The system clock source can be switched between external and internal clock sources
via software using the New Oscillator Source Request (
NOSC) and New Divider Selection Request (
NDIV) bits. The following sources can be selected:
- External Oscillator (EXTOSC)
- EXTOSC with 4x PLL
- High-Frequency Internal
Oscillator (HFINTOSC)
- Low-Frequency Internal Oscillator
(LFINTOSC)
- Secondary Oscillator (SOSC)
The Clock Switch Enable (CSWEN) Configuration bit can be used to enable or
disable the clock switching capability. When CSWEN is set (CSWEN =
1),
writes to
NOSC and
NDIV by user software will allow the system clock to switch
between sources or frequencies. When CSWEN is clear (CSWEN =
0), writes
to NOSC and NDIV are ignored, preventing the system clock from switching from one source
to another.