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<?xml-stylesheet type="text/xsl" href="https://devzone.nordicsemi.com/cfs-file/__key/system/syndication/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>Activating the HFCLK</title><link>https://devzone.nordicsemi.com/f/nordic-q-a/75308/activating-the-hfclk</link><description>Hi 
 We are using an external 32MHz crystal to generate the internal 64MHz clock. 
 As described in several examples, we start the HFCLK with 
 NRF_CLOCK-&amp;gt;TASKS_HFCLKSTART = 1; 
 Now our question is: how can we be shure, that the HFCLK has started correctly</description><dc:language>en-US</dc:language><generator>Telligent Community 13</generator><lastBuildDate>Wed, 19 May 2021 06:37:34 GMT</lastBuildDate><atom:link rel="self" type="application/rss+xml" href="https://devzone.nordicsemi.com/f/nordic-q-a/75308/activating-the-hfclk" /><item><title>RE: Activating the HFCLK</title><link>https://devzone.nordicsemi.com/thread/310299?ContentTypeID=1</link><pubDate>Wed, 19 May 2021 06:37:34 GMT</pubDate><guid isPermaLink="false">137ad170-7792-4731-bb38-c0d22fbe4515:d514d25d-55e1-49fc-b56c-7dc88fa1b5f6</guid><dc:creator>H&amp;#229;kon Alseth</dc:creator><description>&lt;p&gt;Hi,&lt;/p&gt;
&lt;p&gt;&amp;nbsp;&lt;/p&gt;
[quote user=""]&lt;div style="font-family:&amp;#39;Segoe UI&amp;#39;, system-ui, &amp;#39;Apple Color Emoji&amp;#39;, &amp;#39;Segoe UI Emoji&amp;#39;, sans-serif;font-size:14px;font-style:normal;font-weight:400;letter-spacing:normal;text-indent:0;text-transform:none;white-space:normal;"&gt;&lt;span style="color:rgba(51, 153, 102, 1);"&gt;&amp;quot;The EVENTS_HFCLKSTARTED event is generated after the HFXO power up time + the HFXO debounce time has elapsed. It is not allowed to change the value of this register while the HFXO is starting.&amp;quot;&lt;/span&gt;&lt;/div&gt;
&lt;div style="font-family:&amp;#39;Segoe UI&amp;#39;, system-ui, &amp;#39;Apple Color Emoji&amp;#39;, &amp;#39;Segoe UI Emoji&amp;#39;, sans-serif;font-size:14px;font-style:normal;font-weight:400;letter-spacing:normal;text-indent:0;text-transform:none;white-space:normal;"&gt;For us that sounds like the event is generated in every case after HFXO power up time + the HFXO debounce time, even if the clock is not running propperly.&lt;/div&gt;
&lt;div style="font-family:&amp;#39;Segoe UI&amp;#39;, system-ui, &amp;#39;Apple Color Emoji&amp;#39;, &amp;#39;Segoe UI Emoji&amp;#39;, sans-serif;font-size:14px;font-style:normal;font-weight:400;letter-spacing:normal;text-indent:0;text-transform:none;white-space:normal;"&gt;&lt;/div&gt;
&lt;div style="font-family:&amp;#39;Segoe UI&amp;#39;, system-ui, &amp;#39;Apple Color Emoji&amp;#39;, &amp;#39;Segoe UI Emoji&amp;#39;, sans-serif;font-size:14px;font-style:normal;font-weight:400;letter-spacing:normal;text-indent:0;text-transform:none;white-space:normal;"&gt;Can please some one clarify this behaviour for us?&lt;/div&gt;[/quote]
&lt;p&gt;&amp;nbsp;That event will not fire unless the HFXO is present&amp;nbsp;and&amp;nbsp;has been successfully started.&lt;/p&gt;
&lt;p&gt;You can use this event, or you can read the HFCLKSTAT register.&lt;/p&gt;
&lt;p&gt;&lt;/p&gt;
&lt;p&gt;Kind regards,&lt;/p&gt;
&lt;p&gt;Håkon&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>