https://devzone.nordicsemi.com/f/nordic-q-a/76269/what-layer-of-ble-stack-datasheet-mentions-in-crystal-tolerance-sectionHi, NRF52840 datasheet section &quot;5.4.4.2 64 MHz crystal oscillator (HFXO)&quot; mentions crystal tolerances being dependent on packet size. It is not clear to me, what layer of BLE protocol it refers to: L2CAP? ATT? We&#39;re using BLE ATT to exchange ratheren-USTelligent Community 13Mon, 14 Jun 2021 09:45:36 GMThttps://devzone.nordicsemi.com/thread/315067?ContentTypeID=1Mon, 14 Jun 2021 09:45:36 GMT137ad170-7792-4731-bb38-c0d22fbe4515:b3941354-29d3-4f7b-aef3-d738063f5ba7Dennis Melentyev<p>Thank you!</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/315066?ContentTypeID=1Mon, 14 Jun 2021 09:44:55 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d47e6e02-f75a-4a84-acac-c29f26ddc394Kenneth[quote user="Dennis Melentyev"]or fragmented down to ATT_MTU size physical layer packets?[/quote] <p>That is correct.</p> <p>Kenneth</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/315060?ContentTypeID=1Mon, 14 Jun 2021 09:32:53 GMT137ad170-7792-4731-bb38-c0d22fbe4515:a68c7d78-e5eb-46d1-976d-598f53f0c5a4Dennis Melentyev<p>Hi Kenneth,</p> <p>Still, can&#39;t get it: ATT data in your answer is a whole ATT layer packet, or fragmented down to ATT_MTU size physical layer packets?</p> <p>Rephrasing the question: If I set ATT_MTU to 100 bytes and send 250 bytes of data over ATT protocol, will the packet size referenced to in datasheet be &lt;200?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/315058?ContentTypeID=1Mon, 14 Jun 2021 09:22:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:fb5cd6a5-ee05-4bf2-916b-e478382b063aKenneth<p>Hi,</p> <p>This refer to packet length, so &gt;200bytes refer to the entire&nbsp;PDU,&nbsp;including&nbsp;LL header, L2CAP header, ATT data and optional&nbsp;MIC.</p> <p>Kenneth</p><div style="clear:both;"></div>