11.1.1.5 Secondary Oscillator

The Secondary Oscillator (SOSC) is a separate external oscillator block that can be used as an alternate system clock source or as a Timer clock source. The SOSC is optimized for 32.768 kHz and can be used with either an external quartz crystal connected to the SOSCI and SOSCO pins or with an external clock source connected to the SOSCI pin, as shown in the figures below.

Figure 11-5. SOSC 32.768 kHz Quartz Crystal Oscillator Operation
Figure 11-6. SOSC 32.768 kHz External Clock Operation

The SOSC can be enabled through one of two methods:

  • Programming the RSTOSC Configuration bits to select the SOSC as the system clock
  • Programming the NOSC bits to select the SOSC during run time