Internal clocking requirements

[c_han]

hi

I use the S32K chip, the introduction of which says that 80Mhz frequency can be used. Now I look at the clock tree of the chip, I do not know how to select the external crystal oscillator. Can I only select the internal clock if I want to use 80Mhz frequency?

Sorry my English is not good, all the above is translated.Forgive me

[dianabatrlova]

Hi Chun,

I recommend you to take a look at the reference manual in section 28.2 Introduction, RM rev.9.

The S32K has three run modes:

RUN, HSRUN and VLPR

So, we will select RUN mode, because is the normal operating mode for the device out of reset.

In this mode, SYS_CLK can be configured up to max 80 MHz. 

All the related information can be found in section 27.4 Internal clocking requirements and Option 2: Normal RUN

There you can see the configuration of registers where the SYS_CLK is set to 80 MHz and BUS_CLK to 40 MHz.

If you want to reach 80 MHz you need to use PLL. You cannot use internal clock FIRC directly because it generates max 48 MHz.

The SPLL can be sourced by the SOSC reference clock. That is why you need to initialize SOSC clock, SPLL clock, and SCG reference clock.

You can find the code made for the S32K144 you can find in the S32DS File->S32DS Project from Example->S32K144->hello_clocks_s32k144.

The clock settings can be found in clocks_and_modes.c.

I believe it helps you.

Best Regards,

Diana