control register 1
| CPHA | Clock phase  |  
| CPOL | Clock polarity  |  
| MSTR | Master selection  |  
| BR | Baud rate control  |  
| SPE | SPI enable  |  
| LSBFIRST | Frame format  |  
| SSI | Internal slave select  |  
| SSM | Software slave management  |  
| RXONLY | Receive only  |  
| DFF | Data frame format  |  
| CRCNEXT | CRC transfer next  |  
| CRCEN | Hardware CRC calculation enable  |  
| BIDIOE | Output enable in bidirectional mode  |  
| BIDIMODE | Bidirectional data mode enable  |