Control register 3
| EIE | Error interrupt enable  |  
| IREN | IrDA mode enable  |  
| IRLP | IrDA low-power  |  
| HDSEL | Half-duplex selection  |  
| NACK | Smartcard NACK enable  |  
| SCEN | Smartcard mode enable  |  
| DMAR | DMA enable receiver  |  
| DMAT | DMA enable transmitter  |  
| RTSE | RTS enable  |  
| CTSE | CTS enable  |  
| CTSIE | CTS interrupt enable  |  
| ONEBIT | One sample bit method enable  |