Peripherals and clock source

RE: Peripherals and clock source

jcondon — Thu, 04 Aug 2022 16:17:05 GMT

This information belongs in the Product Specification document. A proper clock tree diagram is an important part of MCU documentation.

RE: Peripherals and clock source

Håkon Alseth — Wed, 10 Mar 2021 10:07:34 GMT

Hi,

[quote user="GOAA"]I have a softdevice and I am not enabling HFXO nor HFINT anywhere. So, it will be by default HFCLK and whenever radio is ON, HFXO will be used right?[/quote]

You are correct. The HFXO will then be started only on-demand by the softdevice, and after its done; you will go back to using HFINT.

Cheers,

Håkon

RE: Peripherals and clock source

GOAA — Wed, 10 Mar 2021 07:13:03 GMT

Thanks for your answer,

[quote userid="2115" url="~/f/nordic-q-a/72517/peripherals-and-clock-source/298578#298578"]his clock tree is sourced by the HFCLK, which can be HFXO (external 32M crystal) or HFINT (64 MHz internal RC oscillator)[/quote]

I have a softdevice and I am not enabling HFXO nor HFINT anywhere. So, it will be by default HFCLK and whenever radio is ON, HFXO will be used right?

RE: Peripherals and clock source

Håkon Alseth — Tue, 09 Mar 2021 08:21:38 GMT

Hi,

[quote user=""]What is the clock source used by GPIO and GPIOTE and other such peripherals? What's the clock source used for flash write and RAM operations?[/quote]

The clock source for most* peripherals is always PCLK16M. This clock tree is sourced by the HFCLK, which can be HFXO (external 32M crystal) or HFINT (64 MHz internal RC oscillator).

* some are sourced by the LFCLK, like the RTC peripheral. Same principle applies there; you choose which source for the LFCLK (internal RC, external 32k, or synthesized from HFCLK).

R/W to both RAM and Flash is performed on the CPU speed, ie. 64MHz.

[quote user=""]Is there any site where I can refer what clock source is used by what peripheral?[/quote]

No, unfortunately not. All peripherals that are asynchronous, like UART without hardware flow control, will keep the HFCLK active in sleep.

Kind regards,

Håkon

RE: Peripherals and clock source

Mehmet Nuri — Tue, 09 Mar 2021 02:47:09 GMT

its your choice actually. If you chose to have "high accuracy" interrupts(not work in sleep modes), it will use high frequency xtal. But you can initiate internal 32.768 kHz and have sleep mode enabled interrupts. Depends on your application.