Status of HFCLK after shutting down the radio

[Abdelraouf]

Hi,

I would like to save the most energy when going to sleep mode. In particular, I want to turn off the radio while keeping just RTC timer on.

So, after shutting down the radio, and before executing WFI, do I have to shut down HFCLK also by calling HFCLKSTOP task? Or is it automatically turned off by the MCU when no subsystem is using it?

Thanks in advance.

[Susheel Nuguru]

It is a good practice that if you have started HFCLK in your application, then switch it off when you do not need it. Just to make sure, stopping it when it is already stopped have no effect and should be safe to do. Internally RC HFCLK is turned off when no peripherals that need this clocks are active. RTC does not use HFCLK so you can execute WFI without worrying about it.

[Abdelraouf]

Thanks Aryan!