https://devzone.nordicsemi.com/f/nordic-q-a/10522/does-sev-clear-or-set-the-event-registerDoes SEV() clear or set the Event register? and why do we use it between two WFE() calls? __WFE(); __SEV(); __WFE();en-USTelligent Community 13Wed, 09 Dec 2015 08:50:48 GMThttps://devzone.nordicsemi.com/thread/39141?ContentTypeID=1Wed, 09 Dec 2015 08:50:48 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d2eff0d6-6cae-4f8c-b962-a0bd7bd73345Radoslaw Koppel<p>Please see also my comment here: <a href="https://devzone.nordicsemi.com/question/1555/how-do-you-put-the-nrf51822-chip-to-sleep/?comment=60256#comment-60256">devzone.nordicsemi.com/.../</a> Think twice when are you clearing event flag - the safe place for that operation really depends on the requirements and code itself.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/39140?ContentTypeID=1Fri, 27 Nov 2015 11:00:44 GMT137ad170-7792-4731-bb38-c0d22fbe4515:029a08d9-b331-4c06-8e22-8ed81ce49ea2KnightYusuf<p>now i understand it&#39;s sev()+wfe() that clears the event register not sev() only, thanks</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/39139?ContentTypeID=1Fri, 27 Nov 2015 10:33:23 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d4021e20-12cd-4bb4-be6d-f6f2e16ce9c8Einar Thorsrud<p>Update: Corrected answer.</p> <p>Yes. SEV signals an event. WFE, on the other hand, will put the CPU to sleep and wait for an event, then wake up and clear the event. If&nbsp;the event was already set, WFE will clear the event and return it immediately.</p> <p>This way of using two WFE calls is a power-optimization. See <a href="https://devzone.nordicsemi.com/f/nordic-q-a/49010/methods-to-put-the-nrf52-to-sleep-in-a-spinlock-loop">this thread</a> and <a href="https://devzone.nordicsemi.com/question/58088/nrf51422-wont-sleep/?answer=58214#post-id-58214">this post</a>&nbsp;for details.</p> <p><code> </code></p><div style="clear:both;"></div>