The ‘Null Data Peripheral Write’ mode is specifically designed to simplify DMA operation with the SPI peripheral. The SPI is essentially a simple shift register, clocking a bit of data in and out for each clock period. However, an unusual situation arises when the SPI is configured in master mode, that is, when the SPI is to be the source of the clock, but only received data is of interest. In this case, something must be written to the SPI data register in order to start the SPI data clock and receive the external data. It would be possible to allocate 2 DMA channels, one for data reception, the other to simply feed null, or zero, data into the SPI. However, a more efficient solution was to add a mode that will automatically write a null value to the SPI data register after each data element has been received and transferred by the DMA channel configured for peripheral data reads. The user need only write the initial null value to start the process.