Kinetis MicrocontrollersのトピックRe: System tick timer in stop mode

System tick timer in stop mode

koichimatsuo — Wed, 07 Oct 2015 05:02:59 GMT

Our customer, SONY has one question about System tick timer in stop mode.

They want to understand if they can use SysTick timer to wake up from STOP/PSTOP2 in K22.

The sentence “The System Tick Timer's clock source is always the core clock” is written in 3.2.1.2 System Tick Timer of K22P121M120SF7RM.pdf.

So they believed that SysTick did not function in stop/Pstop2.

But they found one comment of Freescale AE team in last comment of http://community.arm.com/thread/7830 and then they are confusing now.

Extracted Freescale AE team comment from community

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It’s not very clear in the manual, but the systick is actually clocked by the platform clock which is the same frequency as the core clock. We don’t really document the difference between the two very well. Since they are the same frequency most of the time it doesn’t matter, but for low power modes it starts to become important. The platform clock runs in WAIT mode, so it is expected operation for the systick to run in WAIT mode and be able to wake you up. I think the platform clock still be available in STOP mode too, not the BUS clock and this clock's never mentioned in the RM yet.

Again, I checked Table 7-2. Module operation in low power modes of K22P121M120SF7RM.pdf

As the result, I verified that "platform clock" is off in stop mode.

Does anyone comment us?

Re: System tick timer in stop mode

yasuhikokoumoto — Wed, 07 Oct 2015 06:33:31 GMT

Hello koichimatsuo,

in the freescale documents, the platform clock sometimes means the core clock.

Therefore the platform clock in Table 7-2 would not be the same one which had been mentioned by AE team.

To know the truth, you had better check it on the actual board.

Once I checked it on both FRDM-KL25Z and FRDM-K20D50M boards and found SysTick timer had not stopped even in STOP mode.

Please refer to https://community.freescale.com/message/486431#486431 .

There is the same question and answer as you.

Best regards,

Yasuhiko Koumoto.

Re: System tick timer in stop mode

koichimatsuo — Thu, 08 Oct 2015 05:45:17 GMT

Hello Koumoto_san,

Thank you for your prompt response.

According to your comment, I tried. As the result, K22 was woke up by SysTick timer in STOP or PSTOP2 mode...

Umm....

Regards,

Koichi

Re: System tick timer in stop mode

koichimatsuo — Thu, 29 Oct 2015 04:44:36 GMT

Still now I forgot to execute power on reset.

After activating power on reset, I could verify that systick timer was disabled in stop mode.

Unless executing power on reset, IC cannot exit from debug mode.

Step

--------

1) I implemented systick timer's code.

2) Checked if the code have no error and downloaded the image to evaluation board.

3) Removed USB cable due to power on reset.

4) Inserted USB cable.

5) Verified the behavior.

Re: System tick timer in stop mode

yasuhikokoumoto — Thu, 29 Oct 2015 07:53:22 GMT

Hello Koichi Matsuo,

it is very interesting phenomenon.

Please let me know more details.

Is your system running under the debug mode?

Do you say after the power on reset the IC did not enter the debug mode?

If it is true, when did the IC enter the debug mode?

Thank you and best regards,

Yasuhiko Koumoto.

Re: System tick timer in stop mode

yasuhikokoumoto — Thu, 29 Oct 2015 13:36:47 GMT

Hello Koichi Matsuo,

I tried the same thing by my FRDM-KL25Z board.

As the result, you are right.

But it seems that the issue would depend on the power on reset but the program download to the flash.

That is, after downloading, the SysTick did not stop in STOP mode but the SysTick did stop without program download.

When USB is plugged again after program download and push the reset button, the SysTick remain stopping in STOP mode.

Is it the same as your phenomenon?

Best regards,

Yasuhiko Koumoto.

Re: System tick timer in stop mode

koichimatsuo — Fri, 30 Oct 2015 02:31:48 GMT

Hello Koumoto_san,

I'm sorry to respond with a delay.

Yes, I had same phenomenon, too.

Regards,

Koichi