An external clock source can be used as the device system clock by performing one of the following actions:
- Program the RSTOSC[2:0] and FEXTOSC[2:0] bits in the
Configuration Words to select an external clock source that will be used as the default
system clock upon a device Reset.
- Write the NOSC[2:0] and NDIV[3:0]bits to switch the system clock source.