S32KのトピックRe: SAF sBoot CMU_FC Checks

SAF sBoot CMU_FC Checks

ziwu — Tue, 16 Dec 2025 12:32:27 GMT

I don't know how to set the parameters when I config the CMU_FC check in sBoot. I set some values as my understand and generate the code, how are the generated LFREF and HFREF values derived based on the values I set? Can you show the calculation process?

in my opinion, the parameter I set above should compare with RCCR.REF_CNT/ HTCR.HFREF/LTCR.LFREF. if FXOSC=40M, how can I config CMU_FC0 check? when I should set RCCR.REF_CNT/ HTCR.HFREF/LTCR.LFREF? what's the values?

Re: SAF sBoot CMU_FC Checks

danielmartynek — Wed, 17 Dec 2025 11:15:42 GMT

Hello @ziwu,

All the calculations can be found in the S32K3xx RM rev.11

Section 56.5.2 Programming HFREF and LFREF.

Regards,

Daniel

Re: SAF sBoot CMU_FC Checks

ziwu — Fri, 19 Dec 2025 00:55:44 GMT

1. I check the RM Rev.11, I cannot get the result yet, what's the bus clock? is it system clock?

2. I checked the EB tresos, the RCCR set as 0x50 when “Mcu Register Value Optimization” enabled, all RCCR of CMU_FC0/3/4 are 0x50, why they are the same value? I can't get 0x50 by the following formula. How to get 0x50?

Re: SAF sBoot CMU_FC Checks

danielmartynek — Sun, 28 Dec 2025 14:14:26 GMT

Hi @ziwu,

I'm sorry for the delay, I'm currently out of office, and I could not reply earlier.

The system clock should be set precisely to one of the clock options listed in the RM, e.g. Table 157. Option A - High Performance mode (CORE_CLK @ 160 MHz).

Then, Bus clock = Register interface clock = AIPS_SLOW_CLK

I currently cannot test the SAF sBoost driver.

But the thresholds are also calculated and set by the MCAL MCU driver if the CMUs are enabled.

Here is an example for S32DS IDE and RTD 6.0.0:

https://community.nxp.com/t5/S32K-Knowledge-Base/Example-S32K344-MCAL-MCU-ClockMonitor-v1-0-S32DS36-RTD600/ta-p/2179976

Regards,

Daniel

Re: SAF sBoot CMU_FC Checks

ziwu — Mon, 29 Dec 2025 01:10:01 GMT

Got it, thanks