Artesyn ATCA-7365-CE Installation and Use (May 2014) - Manual (Page 174)

Maps and Registers
ATCA-7365-CE Installation and Use (6806800L73J) 174
6.3.4.2.4 Interrupt Identification Register (IIIR)
In order to minimize software overhead during data character transfers, the UART prioritizes
interrupts into four levels (listed in
Table 6-30 ) and records these in the Interrupt Identification
Register. The Interrupt Identification Register (IIR) stores information indicating that a
prioritized interrupt is pending and the source of that interrupt.
Table 6-30 UART Interrupt Priorities
Priority Level Interrupt Source
1 (highest) Receiver Line Status. One or more error bits were set.
2 Received Data is available. In FIFO mode, trigger level was reached; in non-
FIFO mode, RBR has data.
2 Receiver Time out occurred. It happens in FIFO mode only, when there is data
in the receive FIFO but no activity for a time period.
3 Transmitter requests data. In FIFO mode, the transmit FIFO is half or more
than half empty; in non-FIFO mode, THR is read already
4 Modem Status: one or more of the modem input signals has changed state
Table 6-31 Interrupt Identification Register (IIR)
LPC IO Address: Base + 1
Bit Description Default Access
0 Interrupt status bit:
1: no interrupt pending
0: interrupt pending 1 LPC: r
2:1 Interrupt priority level and source:
11: Receiver line status
10: Receiver data available
01: Transmitter holding register empty
00: Modem status 0 LPC: r
3 Time Out Detected:
0: No time out interrupt is pending
1: Character time-out indication (FIFO mode only) 0 LPC: r
5:4 Reserved 0 LPC: r