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  • Case ID: 102852
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In s110 of nrf51882, is HFCLK or LFCLK running?

nrf234

In nRF51 reference manual v2.1 section 18.1.1, it mentioned that the RTC must be able to run while the 16 MHz system clock (SysClk) source is OFF. 2 questions :

Q1: Since RTC0 is used by soft device, does it mean LFCLK is running when SD is active ?

Q2: If LFCLK is running, what's the arm precossor frequence? Is it too slow to communicate with other peripherals ？

Thanks !

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    Hi

    Q1: Yes, the RTC is running and the LFCLK is enabled when the SD is enabled. This is to keep track of time and know when to wake up and start receiving/transmitting packets.

    Q2: I am not sure that I understand your question, but the nRF51 CPU runs on 16MHz HFCLK. When the chip wakes up from either System On or System Off low power modes, the CPU is enabled as well as the 16MHz internal RC oscillator. You can see what clocks and recources different peripherals of the nRF51 require in table 28 in the nRF51822 PS v2.0.

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  • 0

    Hi

    Q1: Yes, the RTC is running and the LFCLK is enabled when the SD is enabled. This is to keep track of time and know when to wake up and start receiving/transmitting packets.

    Q2: I am not sure that I understand your question, but the nRF51 CPU runs on 16MHz HFCLK. When the chip wakes up from either System On or System Off low power modes, the CPU is enabled as well as the 16MHz internal RC oscillator. You can see what clocks and recources different peripherals of the nRF51 require in table 28 in the nRF51822 PS v2.0.

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