Several internal and external
oscillators are provided for generating low to high frequency clocks for use by the
system. The CKM contains all the oscillators in the device and uses them to generate
the system clocks. See the device specific data sheet for whether external
oscillators are available.
Internal Oscillators
- LFOSC: low frequency
oscillator (32kHz typical frequency)
- SYSOSC: system oscillator (up
to 32MHz frequency)
- SYSPLL: system PLL
(phase-locked loop) with programmable frequency (optional)
- USBFLL: USB FLL
(frequency-locked loop) for crystal-less USB operation (optional)
- LFXT: low frequency, low
power crystal oscillator (32kHz typical frequency)
- HFXT: high frequency crystal
oscillator (up to 48MHz typical frequency)
In addition to the oscillators, low frequency (LFCLK_IN) and high frequency
(HFCLK_IN) digital clock inputs are provided to support cases where the LFXT or HFXT
is not used and a direct digital clock is supplied to the device.