https://devzone.nordicsemi.com/f/nordic-q-a/3734/can-i-maintain-a-timer-active-during-off-sleep-state-in-nrf51822Hi all, I&#39;m using the nRF51822-EK (PCA10001) and I&#39;m going to develop a bluetooth cadence (and speed) sensor for MTBs. I desire low power consumption and i though to put the nRF in &quot;system off mode&quot; during inactivity time. The nRF51822 woke up byen-USTelligent Community 13Thu, 04 Sep 2014 17:25:14 GMThttps://devzone.nordicsemi.com/thread/13543?ContentTypeID=1Thu, 04 Sep 2014 17:25:14 GMT137ad170-7792-4731-bb38-c0d22fbe4515:cbf005af-4bad-4c51-8877-ecc20ac12aecPetter Myhre<p>For clarification, the nRF51 Series has two power modes; System ON and System OFF. In System OFF the CPU is always sleeping, while in System ON it may be sleeping.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/13545?ContentTypeID=1Thu, 04 Sep 2014 17:19:36 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d8bf76cf-e985-46ee-852d-8a65de0f6d12Petter Myhre<p>Nikita is correct, also <a href="https://devzone.nordicsemi.com/question/113/32khz-running-in-off-mode-on-nrf51822/">see this</a> for more information. Just for clarification, Low Power mode is a sub power mode of System ON mode.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/13544?ContentTypeID=1Thu, 04 Sep 2014 16:43:16 GMT137ad170-7792-4731-bb38-c0d22fbe4515:99b0587c-54a9-4cf8-a53f-b122ea25575bNikita<p>You can&#39;t use it in system off.</p> <p>But you can use RTC in system on low power mode. In this mode it&#39;ll consume around 3uA = ION + IRTC + IX32k.</p><div style="clear:both;"></div>