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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
765
Universal Asynchronous Receiver-Transmitter (UART)—Intel
®
IXP45X and Intel
®
IXP46X
Product Line of Network Processors
14.5.6
Interrupt Identification Register
In order to minimize software overhead during data character transfers, the UART
prioritizes interrupts into four levels 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.
Register
IER
Bits
Name
Description
31:8
(Reserved)
7
DMAE
DMA Requests Enable:
0 = DMA requests are disabled
1 = DMA requests are enabled
Not used on IXP45X/IXP46X network processors
6
UUE
UART Unit Enable:
0 = the unit is disabled
1 = the unit is enabled
5
NRZE
NRZ coding Enable:
0 = NRZ coding disabled
1 = NRZ coding enabled
Not used on IXP45X/IXP46X network processors
4
RTOIE
Receiver Time Out Interrupt Enable:
0 = Receiver data Time out interrupt disabled
1 = Receiver data Time out interrupt enabled
3
RIE
Modem Interrupt Enable:
0 = Modem Status interrupt disabled
1 = Modem Status interrupt enabled
2
RLSE
Receiver Line Status Interrupt Enable:
0 = Receiver Line Status interrupt disabled
1 = Receiver Line Status interrupt enabled
The DLAB bit in the Line Control Register must be set to logic 0 to access this
register.
1
TIE
Transmit Data request Interrupt Enable:
0 = Transmit FIFO Data Request interrupt disabled
1 = Transmit FIFO Data Request interrupt enabled
0
RAVIE
Receiver Data Available Interrupt Enable:
0 = Receiver Data Available (Trigger level reached) interrupt disabled
1 = Receiver Data Available (Trigger level reached) interrupt enabled
Priority Level
Interrupt origin
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.