CMU mapping in s32k311

[sandeepSingh18606]

I am currently working on configuring the Clock Monitoring Unit (CMU_FC and CMU_FM) and have successfully enabled CMU_FC in RTD, including clock failure notifications.

I have a few questions regarding testing and configuration:

1. Testing Clock Monitoring: I would like to manually test the clock monitoring functionality by directly writing to registers, without using the SAF or SPD packages. Could you please specify which registers can be modified to simulate a clock error?

2. CMU Interrupt Mapping: While configuring interrupts in the Platform module, I see CMU_0, CMU_1, and CMU_2 interrupts available. The reference manual does not clearly map these to CMU0_IRQn, CMU1_IRQn, and CMU2_IRQn. Could you provide this mapping?

3. Interrupt Handler Trigger: The static file contains only one interrupt handler: Mcu_Cmu_ClockFail_IRQHandler. Under what conditions will this specific handler be triggered?

4. CMU_FC and CMU_FM Handler Configuration: I am unable to find clear information in the reference manual regarding which CMU interrupt handler should be configured for the CMU_FC and CMU_FM units. Could you clarify this point?

Thank you for your assistance...............

[sandeepSingh18606]

According to reference manual, failure reaction for CMU_FM1 and CMU_FM2 is interrupt. Destructive reset should not happen.

I think I am observing in below behavior mentioned in reference manual.

I have checked the register also reset reason. I am getting power on reset.
I have configured interrupt in platform module also. still getting above power on reset behavior.

[davidtosenovjan]

A colleague of mine recently shared example code for exactly this:

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

It seems quite straightforward but let me know if some points needs to be clarified.

Hope it helps

[sandeepSingh18606]

Hi David,

Thanks for example code. It is working for me. CMU_FC is working with above example. I am able to simulate CMU errors.

Also, I need support to enable CMU_FM safety mechanism. In S32 design studio, I am not able to see any configuration option for this.

Does S32 design tool supports configuration for CMU_FM, or I need to enable by directly writing to MCU registers?

Please share any example code if available.

[davidtosenovjan]

CMU_FM is not supported in S32DS. 

There is test withing SAF drivers:

https://community.nxp.com/t5/S32K/Example-usage-CMU-FM-1-without-using-MCAL/m-p/2023968

[sandeepSingh18606]

Hi David,

Thank you for sharing the post. I understand you have non-RTD bare metal code, including CMU_FM.

I am currently testing my own bare metal implementation, which works well with the polling method. However, I am facing the same issue with interrupts that you mentioned in your post.

Could you please share your code to resolve the interrupt issue?

[davidtosenovjan]

Please create new support ticket for this:

https://www.nxp.com/support/support:SUPPORTHOME

Thanks for understanding

[sandeepSingh18606]

Hi David,

Thank you for sharing the bare metal code with me. I have reviewed the CMU FM bare metal implementation.

The issue is that the bare metal code directly calls the install_irq_callback function for the CMU FM interrupt, and I am unable to inspect the internal functionality of that callback. Therefore, the bare metal code is not currently helpful for my implementation.

I am using RTD to configure the interrupt and have enabled interrupts for all CMUs (CMU0_IRQn, CMU1_IRQn, CMU2_IRQn) within the platform module. Still, I am encountering a power-on reset issue whenever the interrupt is called.

Separately, I have a quick question: Does the CMU_FM interrupt trigger after every frequency metering operation completes, or does it only trigger when a clock error occurs?

[davidtosenovjan]

After every completion - FMCIE bit enables interrupt for FMC flag (Frequency Meter Operation Complete)

[sandeepSingh18606]

Thank you for the clarification on Intterupt point.

Can you please help me on power on reset issue after Intterupt also.

[davidtosenovjan]

Only following CMUs can be configured to interrupt response:

Regarding your mentions that it is causing POR, it does not make too much sense to me, it is causing destructive reset, not POR.

[sandeepSingh18606]

I have created a support ticket for the same and shared the ticker number with you in private message.

Thanks