Internal Low-Speed Oscillator (ILO)

group group_sysclk_ilo

The ILO operates with no external components and outputs a stable clock at 32.768 kHz nominal.

The ILO is relatively low power and low accuracy. It is available in all power modes and can be used as a source for the Backup domain clock. ../../../_images/sysclk_backup.png

To ensure the ILO remains active in Hibernate mode, and across power-on-reset (POR) or brown out detect (BOD), firmware must call Cy_SysClk_IloHibernateOn().

Additionally, the ILO clock can be trimmed to +/- 1.5% of nominal frequency using a higher precision clock source. Use the Clock Measurement API to measure the current ILO frequency before trimming.


The ILO is always the source clock for the WDT (Watchdog Timer). Therefore:

  • The WDT must be unlocked when making an ILO function call in the PDL

  • It is recommended to always have the ILO enabled

API Reference