https://devzone.nordicsemi.com/f/nordic-q-a/15136/spis-affected-by-uart-settingHi, I have a very sophisticated program on nRF51822 with SD120 which uses SPIS (as an RX for another board) and UART. I used &quot;spi_slave_example&quot; as a base program. I am not sure why the transmitter starts to send data packets for the very first packetsen-USTelligent Community 13Thu, 14 Jul 2016 14:18:23 GMThttps://devzone.nordicsemi.com/thread/57777?ContentTypeID=1Thu, 14 Jul 2016 14:18:23 GMT137ad170-7792-4731-bb38-c0d22fbe4515:aa4104cc-b38c-4fe5-a7a9-b06a34914c19Ole Bauck<p>Do you have constant latency mode enabled, <code>NRF_POWER-&gt;TASKS_CONSTLAT = 1;</code> or does it remove the issue if you enable it? As the spis example states:</p> <pre><code>// Enable the constant latency sub power mode to minimize the time it takes // for the SPIS peripheral to become active after the CSN line is asserted // (when the CPU is in sleep mode). </code></pre><div style="clear:both;"></div>