This blog post provides overview of Clock, PMU and Oscillators/crystals in CYW43907.
Clock
The CPU clock frequencies for APPS core can be configured to one of five options: 60MHz, 80MHz, 120MHz, 160MHz, 320MHz.
PLATFORM_CPU_CLOCK_FREQUENCY parameter must be set to required frequency in file platform_config_bsp_default.h.
For example, to set APPS CPU Frequency to 320MHz , define should be the following
#define PLATFORM_CPU_CLOCK_FREQUENCY PLATFORM_CPU_CLOCK_FREQUENCY_320_MHz
Power Management Unit (PMU)
The Power Management Unit (PMU) core manages power and clock resources for the entire chip, including Clock/reset management and power management.The CYW43907 has an advanced PMU sequencer, which automatically controls the power switches of all resources.
Oscillators/Crystals
CYW43907 uses an external crystal of 37.4 MHz to provide a frequency reference. It is used for generating all radio frequencies and normal operation clocking.
As an alternative to a crystal, an external precision frequency reference can be used, provided that it meets the phase noise requirements. Please refer to the CYW43907 Datasheet for exact requirements.
Along with external crystal, CYW43907 uses a secondary low power oscillator (LPO) for low power mode timing. The internal LPO frequency range is approximately 33 kHz ± 30%, 32.768 kHz to be exact.
