OSC - Oscillator Module (With Fail-Safe Clock Monitor)

The oscillator module contains multiple clock sources and selection features that allow it to be used in a wide range of applications while maximizing performance and minimizing power consumption.

Clock sources can be supplied either internally or externally. External sources include:
Internal sources include:
Special features of the oscillator module include:

The Reset Oscillator (RSTOSC) Configuration bits determine the type of oscillator that will be used when the device runs after a Reset, including when the device is first powered up (see the table below).

Table 1. RSTOSC Selection Table
RSTOSC SFR Reset Values Clock Source
NOSC / COSC NDIV / CDIV OSCFRQ
111 111 0000 (1:1) 0010 (4 MHz) EXTOSC per FEXTOSC
110 110 0010 (4:1) HFINTOSC @ 1 MHz
101 101 0000 (1:1) LFINTOSC
100 100 0000 (1:1) SOSC
011 Reserved
010 010 0000 (1:1) 0010 (4 MHz) EXTOSC + 4x PLL(1)
001 Reserved
000 000 0000 (1:1) 1000 (64 MHz) HFINTOSC @ 64 MHz
Note:
  1. 1.EXTOSC must meet the PLL specifications (see the data sheet Electrical Specifications).
If an external clock source is selected by the RSTOSC bits, the External Oscillator Mode Select (FEXTOSC) Configuration bits must be used to select the External Clock mode. These modes include:

The ECH, ECM and ECL modes rely on an external logic-level signal as the device clock source. The LP, XT and HS modes rely on an external quartz crystal or ceramic resonator as the device clock source. Each mode is optimized for a specific frequency range. The internal oscillator block produces both low-frequency and high-frequency clock signals, designated LFINTOSC and HFINTOSC, respectively. Multiple system operating frequencies may be derived from these clock sources.

The figure below illustrates a block diagram of the oscillator module.

Figure 1. Clock Source Block Diagram