i.MX RT 1170 Systick internal/external source (CLKSOURCE)

[mjbcswitzerland]

Hi All

Does anyone know what the SYSTICK source is when CLKSOURCE is set in SYST_CSR?
From initial quick test it looks like it is clocked by the ARM PLL output (rather than M7_SYSTICK_ROOT).
Is this specified anywhere?

Regards

Mark

[mjbcswitzerland]

Hi Omar

Yes, I have also measured that the core clock looks to be selected when CLKSOURCE  is selected (meaning use the core clock) and when not (external reference clock) I can choose from one of the other sources.

What surprised me is that when using all other i.MX RT parts the CLKSOURCE is usually set to 1 (which is also the core clock, which makes sense, but without further muxing possibilities). Other i.MX RT parts have their external clock source fixed at 24MHz / 240 (100kHz), which makes it unlikely to be used from this source in most cases

At the end of the day it does in fact make sense after the initial surprise at the standard/most typical setting being reversed. I didn't find any SYSTICK example in the 1176 SDK so it made me curious as to why.

Regards

Mark

[Omar_Anguiano]

Hello
Hope you are well.
ARMv7-M documentation suggests that when CLKSOURCE is set the systick uses the processor's clock; this means that if the core is fed from ARM_PLL the systick will also use this source:

If CLKSOURCE is cleared, the systick is fed from any of these sources:

If you have more questions do not hesitate to ask me.
Best regards,
Omar