HFCLK in Pwr Mgmt Example

RE: HFCLK in Pwr Mgmt Example

Sylvain — Thu, 12 Apr 2018 08:24:59 GMT

Ok, thank you for the answer.

RE: HFCLK in Pwr Mgmt Example

Rune Holmgren — Thu, 05 Apr 2018 11:00:49 GMT

Hi,

I talked a bit to my colleagues, and it seems like the register will always be 1 (Running) when you read it out. All ways of reading the register, including debugging, will cause the HFCLK to start. The register is most likely used internally by peripherals which check the state before starting. I am not actually sure why the register is documented at all.

Best regards,
Rune Holmgren

RE: HFCLK in Pwr Mgmt Example

Sylvain — Thu, 05 Apr 2018 10:08:40 GMT

I'm reading it on the register view of Segger when I use the debug mode ...

RE: HFCLK in Pwr Mgmt Example

Rune Holmgren — Thu, 05 Apr 2018 09:28:57 GMT

Hi,

How are you reading HFCLKSTAT->STATE? If you read it with the CPU the result will always be that the HFCLK is on since the CPU will automatically request the HFCLK. Generally, the HFCLK will turn itself off when it is not in use. In table 1 on in the POWER section of the product specification, it's explicitly stated that clocks will not be running after WFE/WFI sets the device into SYSTEM ON IDLE.

I haven't done any tests on hardware now, but it seems from the source code that the example isn't running the HFCLK when the system is in SYSTEM ON IDLE or SYSTEM OFF.

Best regards,
Rune Holmgren