# Precision Internal Low-Speed Oscillator (PILO)¶

group group_sysclk_pilo

PILO provides a higher accuracy 32.768 kHz clock than the ILO.

When periodically calibrated using a high-accuracy clock such as the ECO, the PILO can achieve 250 ppm accuracy of nominal frequency. The PILO is capable of operating in device Active, Sleep and Deep-Sleep power modes. It is not available in Hibernate mode.

The PILO can be used as a source for the Low-Frequency Clock. However, because PILO is disabled in Hibernate mode, RTC timers cannot operate in this mode when clocked using the PILO. Instead, either the ILO or WCO should be used when hibernate operation is required.

Periodic calibration to a high-accuracy clock (such as ECO) is required to maintain accuracy. The application should use the functions described in the Clock Measurement API to measure the current PILO frequency before trimming.