Expand description
Field TXUR writer - Transmitter Underrun interrupt flag. This flag applies only to slave mode (Master = 0). In this case, the transmitter must begin sending new data on the next input clock if the transmitter is idle. If that data is not available in the transmitter holding register at that point, there is no data to transmit and the TXUR flag is set. Data transmitted by the SPI should be considered undefined if TXUR is set.