13.2.4.2.2 PDMA Controlled Mode

In PDMA mode, the interrupts are turned OFF and the PDMA controller uses SPI_X_TXRFM and SPI_X_RXAVAIL signals to govern the filling and emptying of the FIFOs. The SPI_X_RXAVAIL signal indicates that the data is available to be read and SPI_X_TXRFM indicates that the transmit is done and it is ready to receive more data.

For example, consider the transmission of 64 KB of data to an external EEPROM from a PDMA controlled SPI controller. The data frame size is set to eight and the number of data frames 
per- transfer is set to one. The transmit FIFO is repeatedly filled and emptied by the PDMA engine, using the SPI_X_TXRFM and SPI_X_RXAVAIL signals. In PDMA mode, the transmit done and receive data available interrupts are masked, and the PDMA engine is used to notify the application on completion.