Serial Status Register
| TBI | Transmit bus idle flag bit (Effective only when DMA mode is enabled) |
| TDRE | Transmit data empty flag bit |
| RDRF | Received data full flag bit |
| ORE | Overrun error flag bit |
| TBIE | Transmit bus idle interrupt enable bit (Effective only when DMA mode is enabled) |
| DMA | DMA mode enable bit |
| TSET | Transmit empty flag set bit |
| REC | Received error flag clear bit |