5.1.1 Clock Selection

The PIC16F, PIC18F and PIC32CM MCUs offer flexible and robust clock systems that support multiple internal and external clock sources, programmable prescalers and safe run-time switching. The PIC16F, PIC18F and PIC32CM MCUs allow peripherals to request and receive clocks as needed, support low-frequency and high-frequency oscillators, and provide mechanisms for clock accuracy tuning and failure detection. The main clock can be prescaled, and peripherals can operate either synchronously or asynchronously with respect to the main clock. These features enable efficient power management, high performance and reliable operation across a wide range of applications.

The main difference between PIC16F, PIC18F and PIC32CM is in the way clock management is integrated within the MCU. The PIC16F and PIC18F MCUs use the device configuration bits and an Oscillator Module (OSC), while the PIC32CM MCUs (depending on the family of devices) implement a Clock System that uses a combination of the Generic Clock Controller (GCLK), Main Clock Controller (MCLK), System Controller (SYSCTRL), Oscillator Controllers (OSCCTRL, OSC32KCTRL) and Power Manager (PM). Table 5-3 provides a comparison of features between PIC16F, PIC18F and PIC32CM.