The MCUXpresso SDK provides APIs for MCUXpresso SDK devices' clock operation.

Get frequency

A centralized function CLOCK_GetFreq gets different clock type frequencies by passing a clock name. For example, pass a kCLOCK_CoreSysClk to get the core clock and pass a kCLOCK_BusClk to get the bus clock. Additionally, there are separate functions to get the frequency. For example, use CLOCK_GetCoreSysClkFreq to get the core clock frequency and CLOCK_GetBusClkFreq to get the bus clock frequency. Using these functions reduces the image size.

External clock frequency

The external clocks EXTAL0/EXTAL1/EXTAL32 are decided by the board level design. The Clock driver uses variables g_xtal0Freq/g_xtal1Freq/g_xtal32Freq to save clock frequencies. Likewise, the APIs CLOCK_SetXtal0Freq, CLOCK_SetXtal1Freq, and CLOCK_SetXtal32Freq are used to set these variables.
The upper layer must set these values correctly. For example, after OSC0(SYSOSC) is initialized using CLOCK_InitOsc0 or CLOCK_InitSysOsc, the upper layer should call the CLOCK_SetXtal0Freq. Otherwise, the clock frequency get functions may not receive valid values. This is useful for multicore platforms where only one core calls CLOCK_InitOsc0 to initialize OSC0 and other cores call CLOCK_SetXtal0Freq.