https://devzone.nordicsemi.com/f/nordic-q-a/8982/the-frequency-is-low-when-nrf51822-connected-jlink-via-swdIf I want to connect the NRF51822 board to Keil using JLink via SWD, I found the SW&#39;s clock frequency must below 20kHz. If I choose the higher frequency, the Keil can not scan the chip. Any suggestion? P.S. The SWDIO is connected directly, and SWCLKen-USTelligent Community 13Tue, 01 Sep 2015 11:17:56 GMThttps://devzone.nordicsemi.com/thread/33067?ContentTypeID=1Tue, 01 Sep 2015 11:17:56 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0ccac55b-8149-4260-a92b-137f5494e63dMartinBL<p>Hi.</p> <ul> <li>Is this a custom board or a development kit?</li> <li>What nRF51 revision are you using? Refer to the <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf51.v1.0.0/pdflinks/nrf51_comp_matrix.html?resultof=%22%63%6f%6d%70%61%74%69%62%69%6c%69%74%79%22%20%22%63%6f%6d%70%61%74%22%20">compatibility matrix</a>.</li> <li>What sort of debugger do you use?</li> <li>If it is a custom board can you please edit your question and include a schematic and preferably your PCB layout? You can create a support ticket on our support portal, <a href="https://www.nordicsemi.com/eng/Support-Community">MyPage</a>, if you want confidentiality.</li> </ul><div style="clear:both;"></div>