title: Setting nss_soft in Master (SPI)
body: <p>I want to set the <a href="https://www.st.com/resource/en/application_note/dm00725181-enhanced-methods-to-handle-spi-communication-on-stm32-devices-stmicroelectronics.pdf" rel="nofollow noreferrer">NSS</a> pin to software mode in master using <a href="https://en.wikipedia.org/wiki/STM32#Nucleo_boards" rel="nofollow noreferrer">Nucleo</a> STM32F103RB.</p>
  <p>In the reference manual, they say,</p>
  <blockquote>
  <p>In NSS Software mode, set the SSM and SSI bits in the SPI_CR1 register. If the NSS pin is required in output mode, the SSOE bit only should be set.</p>
  </blockquote>
  <p>Why do we need to set the SSI bit with SSM?</p>
  <p>What is the purpose of the SSOE bit?</p>