Serial interface FIFO enables
| U0TXFIFOEN | USART0 transmitter FIFO enable |
| U1TXFIFOEN | USART1 transmitter FIFO enable |
| U2TXFIFOEN | USART2 transmitter FIFO enable |
| U3TXFIFOEN | USART3 transmitter FIFO enable |
| SPI0TXFIFOEN | SPI0 transmitter FIFO enable |
| SPI1TXFIFOEN | SPI1 transmitter FIFO enable |
| RESERVED | Reserved |
| RESERVED | Reserved |
| U0RXFIFOEN | USART0 receiver FIFO enable |
| U1RXFIFOEN | USART1 receiver FIFO enable |
| U2RXFIFOEN | USART2 receiver FIFO enable |
| U3RXFIFOEN | USART3 receiver FIFO enable |
| SPI0RXFIFOEN | SPI0 receiver FIFO enable |
| SPI1RXFIFOEN | SPI1 receiver FIFO enable |
| RESERVED | Reserved |