Control register 1
| UE | USART enable |
| UESM | USART enable in Stop mode |
| RE | Receiver enable |
| TE | Transmitter enable |
| IDLEIE | IDLE interrupt enable |
| RXNEIE | RXNE interrupt enable |
| TCIE | Transmission complete interrupt enable |
| TXEIE | interrupt enable |
| PEIE | PE interrupt enable |
| PS | Parity selection |
| PCE | Parity control enable |
| WAKE | Receiver wakeup method |
| M0 | Word length |
| MME | Mute mode enable |
| CMIE | Character match interrupt enable |
| OVER8 | Oversampling mode |
| DEDT0 | DEDT0 |
| DEDT1 | DEDT1 |
| DEDT2 | DEDT2 |
| DEDT3 | DEDT3 |
| DEDT4 | Driver Enable de-assertion time |
| DEAT0 | DEAT0 |
| DEAT1 | DEAT1 |
| DEAT2 | DEAT2 |
| DEAT3 | DEAT3 |
| DEAT4 | Driver Enable assertion time |
| RTOIE | Receiver timeout interrupt enable |
| EOBIE | End of Block interrupt enable |
| M1 | Word length |