Interrupt Enable.
| RX_OV_CH0 | Enable for RX FIFO Overrun interrupt. |
| RX_THD_CH0 | Enable for interrupt when RX FIFO reaches the number of bytes configured by the RXTHD field. |
| TX_OB_CH0 | Enable for interrupt when TX FIFO has only one byte remaining. |
| TX_HE_CH0 | Enable for interrupt when TX FIFO is half empty. |