topic KL82 RTC load capacitance setting in Kinetis Microcontrollers https://community.nxp.com/t5/Kinetis-Microcontrollers/KL82-RTC-load-capacitance-setting/m-p/643498#M39019 <HTML><HEAD></HEAD><BODY><P>I have this crystal as my rtc timer clock:&nbsp;<A class="link-titled" href="http://www.digikey.ca/product-detail/en/ndk/NX2012SA-32.768K-STD-MUB-1/644-1219-1-ND/4914462" title="http://www.digikey.ca/product-detail/en/ndk/NX2012SA-32.768K-STD-MUB-1/644-1219-1-ND/4914462">NX2012SA-32.768K-STD-MUB-1 NDK | Crystals, Oscillators, Resonators | DigiKey</A>&nbsp; for a KL82 micro controller. Any the RTC is drifting a lot. So I looked into the datasheets and found load capacitance setting on page 1299 of the manual:</P><P><span class="lia-inline-image-display-wrapper" image-alt="微信截图_20161202121913.png"><img src="https://community.nxp.com/t5/image/serverpage/image-id/8930iBB746A73359CB6B4/image-size/large?v=v2&amp;px=999" role="button" title="微信截图_20161202121913.png" alt="微信截图_20161202121913.png" /></span></P><P>cause there is no 12.5pf setting, should I enable SC16P bit or should I enable both SC8P and SC4P?</P><P>What's the meaning of enable the additional load? When I set these bits, do they enable the cap inside mcu or just tell the mcu we have a crystal which has this amount of load capacitance?</P><P></P><P></P><P>Thank you very in advance.</P><P></P><P></P><P>Best,</P></BODY></HTML> Fri, 02 Dec 2016 17:24:43 GMT diandizhu 2016-12-02T17:24:43Z KL82 RTC load capacitance setting https://community.nxp.com/t5/Kinetis-Microcontrollers/KL82-RTC-load-capacitance-setting/m-p/643498#M39019 <HTML><HEAD></HEAD><BODY><P>I have this crystal as my rtc timer clock:&nbsp;<A class="link-titled" href="http://www.digikey.ca/product-detail/en/ndk/NX2012SA-32.768K-STD-MUB-1/644-1219-1-ND/4914462" title="http://www.digikey.ca/product-detail/en/ndk/NX2012SA-32.768K-STD-MUB-1/644-1219-1-ND/4914462">NX2012SA-32.768K-STD-MUB-1 NDK | Crystals, Oscillators, Resonators | DigiKey</A>&nbsp; for a KL82 micro controller. Any the RTC is drifting a lot. So I looked into the datasheets and found load capacitance setting on page 1299 of the manual:</P><P><span class="lia-inline-image-display-wrapper" image-alt="微信截图_20161202121913.png"><img src="https://community.nxp.com/t5/image/serverpage/image-id/8930iBB746A73359CB6B4/image-size/large?v=v2&amp;px=999" role="button" title="微信截图_20161202121913.png" alt="微信截图_20161202121913.png" /></span></P><P>cause there is no 12.5pf setting, should I enable SC16P bit or should I enable both SC8P and SC4P?</P><P>What's the meaning of enable the additional load? When I set these bits, do they enable the cap inside mcu or just tell the mcu we have a crystal which has this amount of load capacitance?</P><P></P><P></P><P>Thank you very in advance.</P><P></P><P></P><P>Best,</P></BODY></HTML> Fri, 02 Dec 2016 17:24:43 GMT https://community.nxp.com/t5/Kinetis-Microcontrollers/KL82-RTC-load-capacitance-setting/m-p/643498#M39019 diandizhu 2016-12-02T17:24:43Z Re: KL82 RTC load capacitance setting https://community.nxp.com/t5/Kinetis-Microcontrollers/KL82-RTC-load-capacitance-setting/m-p/643499#M39020 <HTML><HEAD></HEAD><BODY><P>46.4.1.1 Oscillator control<BR />The 32.768 kHz crystal oscillator is disabled at VBAT POR and must be enabled by<BR />software. After enabling the cystal oscillator, wait the oscillator startup time before<BR />setting SR[TCE] or using the oscillator clock external to the RTC.<BR /><STRONG>The crystal oscillator includes tunable capacitors that can be configured by software. Do</STRONG><BR /><STRONG>not change the capacitance unless the oscillator is disabled.</STRONG></P></BODY></HTML> Tue, 06 Dec 2016 21:56:12 GMT https://community.nxp.com/t5/Kinetis-Microcontrollers/KL82-RTC-load-capacitance-setting/m-p/643499#M39020 diandizhu 2016-12-06T21:56:12Z