configuration register 1
| DSIZE | Number of bits in at single SPI data frame | 
| FTHVL | threshold level | 
| UDRCFG | Behavior of slave transmitter at underrun condition | 
| UDRDET | Detection of underrun condition at slave transmitter | 
| RXDMAEN | Rx DMA stream enable | 
| TXDMAEN | Tx DMA stream enable | 
| CRCSIZE | Length of CRC frame to be transacted and compared | 
| CRCEN | Hardware CRC computation enable | 
| MBR | Master baud rate |