Why can't the FCCU of FS26 on the S32K3X4EVB-T172 be configured as LOW Error?

[Allen_863]

I configured FCCU's FAULT POLARITY to HIGH LEVEL, and then used Dio_WriteChannel to output LOW to maintain a NORMAL state. Outputting HIGH to trigger an error and it works

However, when I configured FCCU's FAULT POLARITY to LOW LEVEL and then used Dio_WriteChannel to output HIGH to maintain a NORMAL state, the measurement results for FCCU were not HIGH, but rather alternated between LOW and HIGH. Why?

[petervlna]

Hello,

I configured FCCU's FAULT POLARITY to HIGH LEVEL, and then used Dio_WriteChannel to output LOW to maintain a NORMAL state.

Once you configure FCCU to drive pins, it will overtake the signal to the pin. Your SUIL will not output the GPIO on the pin output.

It will be driven by FCCU.

However, when I configured FCCU's FAULT POLARITY to LOW LEVEL and then used Dio_WriteChannel to output HIGH to maintain a NORMAL state, the measurement results for FCCU were not HIGH, but rather alternated between LOW and HIGH. Why?

Not sure. Isn't the device resetting?

I am not clear about your test case. Why would you drive pins controlled by FCCU by other peripherals (SIUL). Are you reconfiguring the SIUL to drive the pin from SIUL instead of FCCU on the fly or... ?

Best regards,

Peter

[Allen_863]

My understanding of the FCCU is that it's a digital input to the FS26, so the MCU must output signals to the FS26. The FS26's FCCU fault polarity setting determines which signals are considered faulty. Therefore, when the FCCU fault polarity is configured as LOW (indicating low is error), the MCU should output HIGH (indicating no error)

Is the FCCU controlled by the FS26 itself? If so, why does the datasheet indicate that the FCCU is a digital input ?

Configuring the FCCU FAULT POLARITY to LOW is error, Therefore, MCU needs to output HIGH so that the FS26 won't interpret it as an error (LOW is an error). However, I see the S32K3 keeps resetting. This is because I set the S32K3 to output HIGH, but the signal measured by the FCCU isn't 100% HIGH; instead, it's alternating between HIGH and LOW, which is why the FS26 interprets it as an error.

However, I don't understand why when I output LOW to the FCCU using the S32K3, I can measure 100% LOW, but when I output HIGH to the FCCU using the S32K3, it shows alternating HIGH/LOW instead of 100% HIGH?

[petervlna]

Hello,

My understanding of the FCCU is that it's a digital input to the FS26, so the MCU must output signals to the FS26. Therefore, when the FCCU fault polarity is configured as LOW (indicating low is error), the MCU should output HIGH (indicating no error)

Yes, that is correct.

Is the FCCU controlled by the FS26 itself? If so, why does the datasheet indicate that the FCCU is a digital input ?

No. FCCU output signals (EOUT) are controlled by FCCU module based on the configuration of the FCCU.

Configuring the FCCU FAULT POLARITY to LOW is error, Therefore, MCU needs to output HIGH so that the FS26 won't interpret it as an error (LOW is an error). However, I see the S32K3 keeps resetting.

Is it only resetting? Or there is FS26 cutting power to S32K3 due to the FCCU fault like active? (so the Power on reset)

You can also see the reset reason in the S32K3 RGM[DES/FES] registers after the reset. Also if the root cause is FCCU you will also see in the NCFS register set flag.

However, I don't understand why when I output LOW to the FCCU using the S32K3, I can measure 100% LOW, but when I output HIGH to the FCCU using the S32K3, it shows alternating HIGH/LOW instead of 100% HIGH?

I am not clear here. But the alternating can be caused also by resetting of the device. Depends if you also measure reset line and voltages at the same time. 

Or just the EOUT.

Also is the behavior present in the same uC config but with the FS26 in debug mode?

Could you provide more information on the issue?

Best regards,

Peter

[Allen_863]

I noticed that I shouldn't be using DIO as output to the FS26. I should configure the S32K3's pins to FCCU.

It seems I need to purchase the S32 Safety Software Framework (SAF) and Safety Peripheral Drivers (SPD) to use the FCCU driver?

I know why the FCCU is showing alternating HIGH and LOW signals. It's because I didn't configure the initial value to HIGH, so the FS26 will immediately reset whenever it encounters LOW upon startup.

[petervlna · Accepted solution]

Hello,

It seems I need to purchase the S32 Safety Software Framework (SAF) and Safety Peripheral Drivers (SPD) to use the FCCU driver?

Just for FCCU is enough to have SPD. But SAF also covers it.

eMCEM include FCCU drivers.

Best regards,

Peter