Clock debugging

[smathad]

Hi NXP community, 

I have a couple of questions regarding debugging of the clock on Kinetis K24. 

We want to check the stability and jitter of the clock on the 48MIRC. Hence, we want to be able to measure all the clocks before and after the change from the 8MHz external crystal (currently in use) to the 48MIRC. 

1. I understand from the reference manual that we can check the system/core clock using trace_clkout on PORTE 0th pin.  Please correct me if I am wrong. 

2. Is there anyway I can probe the other clocks- bus clock, flex clock and flash clock? Please let me know the modules and the pins if there is any such provision. 

Regards,

Sachin

[mjbcswitzerland · Accepted solution]

Hi Sachin

The clock sources that can be connected to CLKOUT are

Beware that PTE0 is RTC_CLKOUT and not CLKOUT. CLKOUT can be assigned to either PTC3 or to PTA6.

Regards

Mark

[uTasker project developer for Kinetis and i.MX RT]

[smathad]

Hi Mark,

Thank you for your response!! 

CLKOUT pin will help me with my clock monitoring for sure.

I also noticed that there is trace clock selection option (TRACE_CLKOUT) available on 1st pin other than the RTC clock. 

Q. How is trace clock different from clock out ?

    a. Is it correct to understand that trace clock can be used only when I boot my system with the debugger and clock out (CLKOUT) can be used in normal run mode? 

  b. Any advantage using one over the other (TRACE_CLKOUT vs CLKOUT) ? 

Regards,

Sachin 

[mjbcswitzerland]

Sachin

I blieve that the trace clock is used when a trace module is connected for debugging - whereby the clock used as reference for that module can be selected.

As it states you could also connect the core clock to that pin, which would presumably allow it to be "observed".

Regards

Mark