| Bits | Description |
|---|---|
| 7 | Reserved must be zero |
| 6 | UART1 Tx empty |
| 5 | UART1 Rx near full \ shared |
| 4 | UART1 Rx available / interrupt |
| 3 | Reserved must be zero |
| 2 | UART0 Tx empty |
| 1 | UART0 Rx near full \ shared |
| 0 | UART0 Rx available / interrupt |
* Rx near full overrides Rx available
* If a device interrupt is disabled, it enters a polled mode