Interrupt Enable control register
| RX_FERR | Enable Interrupt For RX Frame Error |
| RX_PAR | Enable Interrupt For RX Parity Error |
| CTS_EV | Enable Interrupt For CTS signal change Error |
| RX_OV | Enable Interrupt For RX FIFO Overrun Error |
| RX_THD | Enable Interrupt For RX FIFO reaches the number of bytes configured by RXTHD |
| TX_OB | Enable Interrupt For TX FIFO has one byte remaining |
| TX_HE | Enable Interrupt For TX FIFO has half empty |