topic Re: FLEXIO in S32K

FLEXIO

GXY — Sun, 07 Sep 2025 05:16:19 GMT

The development board I use is S32K144. I found a discrepancy with the manual when I used the FLEXIO function. In the manual about power management mode, it is said that FLEXIO does not work in VLPS, but I found that the FLEXIO timer can still be used after entering VLPS. My experiment is to use a pin as a trigger to trigger the timer to output a waveform. Another experiment is to configure it as serial port reception. I use PC serial port connection tool to connect to the corresponding pin. After entering VLPS mode, I can still trigger an interrupt to wake up MCU by sending a byte of data, and the data I read in the shifterbuffer in the interrupt service program is really a byte of data I send. The above two experiments can prove that the FLEIXO module can still run in VLPS mode, which is contrary to the manual. So can anyone answer my question

Re: FLEXIO

davidtosenovjan — Mon, 08 Sep 2025 12:49:20 GMT

Where is it stated that FlexIO cannot ryn in VLPS mode? I haven't found such statement - could you clarify? Thanks

Re: FLEXIO

GXY — Sun, 14 Sep 2025 12:08:38 GMT

It is mentioned in a table in Chapter 39 POWERMANAGER of the manual that FLEXIO is OFF in VLPS, which means it cannot be used

Re: FLEXIO

davidtosenovjan — Mon, 15 Sep 2025 07:43:59 GMT

Could you double check power mode status. Possibly different way that using debugger, as it may not reflect it according note below:

Re: FLEXIO

GXY — Thu, 09 Oct 2025 11:22:42 GMT

I cannot view the value of this register in VLPS mode, and this bit will not be updated to STOP or VLPS. What I can confirm is that the CPU has not continued to execute the program, and the return value of the POWER_SYS_SetMode() function is SUCCESS after waking up. I think this indicates that the VLPS mode has been successfully entered. As I said before, before entering VLPS, I have configured one pin of FLEXIO to receive the serial port and turned on the interrupt of the SSF flag. After entering the VLPS, I can still wake up the MCU by sending a byte of serial port data. I read the data of the shift buffer in the interrupt exactly as I sent it. The above phenomenon indicates that FLEXIO is still working in the VLPS mode. I think this is inconsistent with OFF in the manual table, so I want to know what the problem is.

Re: FLEXIO

davidtosenovjan — Fri, 10 Oct 2025 08:05:06 GMT

Actually I have discussed it here and conclusion is (confirmed by design with similar case) that if Table 39-4 states OFF for certain module and power mode, it is not allowed to use it.

It is not controller characteristic but system requirement i.e. something needed to be guaranteed by user.

Re: FLEXIO

GXY — Mon, 13 Oct 2025 08:43:36 GMT

If it's as you said, then in the FlexIO column of the AWIC's wake-up sources in Table 8-5, VLPS should be added like for some other modules, but it's not. So I believe that the OFF state in Table 39-4 is as described in Table 39-3 (Module and clock sources are disabled.). I have verified that other modules, such as (EWM), are OFF under VLPS, and do not generate interrupts after entering VLPS without refreshing the configuration. In summary, I still believe that according to the manual, FLEXIO should not work under VLPS, but my tests show otherwise. I confirmed that the MCU indeed entered VLPS mode through the following three points: 1. The bus clock was turned off (observed with an oscilloscope through clkout). 2. The CPU did not continue executing the program (this program referenced a demo program for mode conversion). 3. After waking up, the third bit of SMC->PMCTRL printed out was 0, indicating that the VLPS process was not aborted

Re: FLEXIO

davidtosenovjan — Tue, 14 Oct 2025 11:52:28 GMT

Even if it could work under certain conditions, it was not validated, so, it must not be used. I don't see any issue with Table 8-5, it is correct.