Channel Status Register
| RXRDY | Receiver Ready (cleared by reading US_RHR) |
| TXRDY | Transmitter Ready (cleared by writing US_THR) |
| ENDRX | End of RX Buffer (cleared by writing US_RCR or US_RNCR) |
| ENDTX | End of TX Buffer (cleared by writing US_TCR or US_TNCR) |
| OVRE | Overrun Error (cleared by writing a one to bit US_CR.RSTSTA) |
| TXEMPTY | Transmitter Empty (cleared by writing US_THR) |
| UNRE | Underrun Error (cleared by writing a one to bit US_CR.RSTSTA) |
| TXBUFE | TX Buffer Empty (cleared by writing US_TCR or US_TNCR) |
| RXBUFF | RX Buffer Full (cleared by writing US_RCR or US_RNCR) |