The CC27xx devices have the following internal system clocks.
- The 96MHz HFCLK is used as the main system (MCU and peripherals) clock. This is driven by the internal 96MHz RC Oscillator (HFOSC), which can track its accuracy against an external 48MHz crystal (HFXT). The HFOSC tracking loop is enabled by default by the system ROM bootcode. Radio and ADC operate with the external 48MHz crystal oscillator.
- The 32.768kHz LFCLK is used as the internal low-frequency system clock. It is used for the RTC, the watchdog timer (if enabled in standby power mode), and to synchronize the radio timer after exiting Standby power mode. LFCLK can be driven by the internal 30-34kHz RC Oscillator (LFOSC), a 32.768kHz watch-type crystal, or clock input in LFXT bypass mode. When using a crystal or the internal RC oscillator, the device can output the 32kHz LFCLK signal to other devices, thereby reducing the overall system cost.
- The 80/90.3168/98.304 MHz AFOSC (Auxiliary Frequency Oscillator) is used as the high-frequency clock for generating needed frequencies to support for CAN-FD and audio I2S operations. The AFOSC tracks the HFOSC which in turn, tracks its accuracy against the external 48MHz crystal (HFXT). AFOSC can generate 80, 90.3168, and 98.304MHz clock frequencies with a 10ppb tracking accuracy from HFOSC.