48.7.7.7.1 TDRE and RDRF Configuration

In Multiple Data mode, it is possible to write one or more data in the same SPI_TDR/SPI_RDR access. The TDRE flag indicates if one or more data can be written in the FIFO depending on the configuration of SPI_FMR.TXRDYM/RXRDYM.

As an example, if two data are written each time in SPI_TDR, it is useful to configure the TXRDYM field to the value ‘1’ so that the TDRE flag is at ‘1’ only when at least two data can be written in the Transmit FIFO.

Similarly, if four data are read each time in SPI_RDR, it is useful to configure the RXRDYM field to the value ‘2’ so that the RDRF flag is at ‘1’ only when at least four unread data are in the Receive FIFO.