Agilex™ 7 Hard Processor System Technical Reference Manual
21.4.6. Interrupts
The assertion of the UART interrupt output signal occurs when one of the following interrupt types are enabled and active: †
| Interrupt Type | Priority | Source | Interrupt Reset Control | 
|---|---|---|---|
| Receiver line status | Highest | Overrun, parity and framing errors, break condition. | Reading the line status Register. | 
| Received data available | Second | Receiver data available (FIFOs disabled) or RCVR FIFO trigger level reached (FIFOs enabled). | Reading the receiver buffer register (FIFOs disabled) or the FIFO drops below the trigger level (FIFOs enabled) | 
| Character timeout indication | Second | No characters in or out of the Receive FIFO during the last 4 character times and there is at least 1 character in it during this Time. | Reading the receiver buffer Register. | 
| Transmit holding register empty | Third | Transmitter holding register empty (Programmable THRE Mode disabled) or Transmit FIFO at or below threshold (Programmable THRE Mode enabled). | Reading the IIR register (if source of interrupt); or, writing into THR (FIFOs or Programmable THRE Mode not enabled) or Transmit FIFO above threshold (FIFOs and Programmable THRE Mode enabled). | 
| Modem Status | Fourth | Clear to send or data set ready or ring indicator or data carrier detect. If auto flow control mode is enabled, a change in CTS (that is, DCTS set) does not cause an interrupt. | Reading the Modem status Register. | 
You can enable the interrupt types with the interrupt enable register (IER_DLH).
Once an interrupt is signaled, you can determine the interrupt source by reading the Interrupt Identity Register (IIR).