24.3.2.2.2 SPI Frame Formats

The serial frame in SPI mode is defined to be one character of eight data bits. The USART in master SPI mode has two valid frame formats:

  • 8-bit data, MSb first
  • 8-bit data, LSb first

The data order is selected by writing to the Data Order bit (UDORD) in the Control C register (USARTn.CTRLC).

After a complete frame is transmitted, a new frame can directly follow it, or the communication line can return to the idle (high) state.