An example of SPI_CSR programming:
// Data transfer parameters
SPI0->SPI_CSR[0] = SPI_CSR_CPOL // Inactive state value of SPCK is logic level one
| SPI_CSR_NCPHA // Data is captured on the leading edge of SPCK and changed on the following edge
| SPI_CSR_CSNAAT // Chip select active after transfer
| SPI_CSR_BITS_12_BIT // Bits per transfer
| SPI_CSR_SCBR(100) // bit rate
| SPI_CSR_DLYBS(100); // delay from NPCS falling edge (activation)