control register 1
| SPE | Serial Peripheral Enable |
| MASRX | Master automatic SUSP in Receive mode |
| CSTART | Master transfer start |
| CSUSP | Master SUSPend request |
| HDDIR | Rx/Tx direction at Half-duplex mode |
| SSI | Internal SS signal input level |
| CRC33_17 | 32-bit CRC polynomial configuration |
| RCRCI | CRC calculation initialization pattern control for receiver |
| TCRCI | CRC calculation initialization pattern control for transmitter |
| IOLOCK | Locking the AF configuration of associated IOs |