Control register 1
| SBK | Send break |
| RWU | Receiver wakeup |
| RE | Receiver enable |
| TE | Transmitter enable |
| IDLEIE | IDLE interrupt enable |
| RXNEIE | RXNE interrupt enable |
| TCIE | Transmission complete interrupt enable |
| TXEIE | TXE interrupt enable |
| PEIE | PE interrupt enable |
| PS | Parity selection |
| PCE | Parity control enable |
| WAKE | Wakeup method |
| M | Word length |
| UE | USART enable |
| OVER8 | Oversampling mode |