MODE=USART_EXT_CLK
USART Control A
| SWRST | Software Reset  |  
| ENABLE | Enable  |  
| MODE | Operating Mode 0 (USART_EXT_CLK): USART mode with external clock 1 (USART_INT_CLK): USART mode with internal clock 2 (SPI_SLAVE): SPI mode with external clock 3 (SPI_MASTER): SPI mode with internal clock 4 (I2C_SLAVE): I2C mode with external clock 5 (I2C_MASTER): I2C mode with internal clock  |  
| RUNSTDBY | Run during Standby  |  
| IBON | Immediate Buffer Overflow Notification  |  
| SAMPR | Sample  |  
| TXPO | Transmit Data Pinout  |  
| RXPO | Receive Data Pinout  |  
| SAMPA | Sample Adjustment  |  
| FORM | Frame Format  |  
| CMODE | Communication Mode  |  
| CPOL | Clock Polarity  |  
| DORD | Data Order  |