Interrupt Enable Register.
| FRAMIE | Enable for RX Frame Error Interrupt. |
| PARITYIE | Enable for RX Parity Error interrupt. |
| OVERIE | Enable for RX FIFO OVerrun interrupt. |
| FFRXIE | Enable for interrupt when RX FIFO reaches the number of bytes configured by the RXTHD field. |
| FFTXOIE | Enable for interrupt when TX FIFO has only one byte remaining. |
| FFTXHIE | Enable for interrupt when TX FIFO reaches half the number of bytes allowed in the fifo or less. |