UM10503
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User manual
Rev. 1.3 — 6 July 2012
955 of 1269
NXP Semiconductors
UM10503
Chapter 37: LPC43xx USART0_2_3
37.6.5 USART Interrupt Identification Register
IIR provides a status code that denotes the priority and source of a pending interrupt. The
interrupts are frozen during a IIR access. If an interrupt occurs during a IIR access, the
interrupt is recorded for the next IIR access.
Bits IIR[9:8] are set by the auto-baud function and signal a time-out or end of auto-baud
condition. The auto-baud interrupt conditions are cleared by setting the corresponding
Clear bits in the Auto-baud Control Register.
9
ABTOINTEN
Enables the auto-baud time-out interrupt.
0
0
Disable auto-baud time-out Interrupt.
1
Enable auto-baud time-out Interrupt.
31:10 -
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
Table 826. USART Interrupt Enable Register when DLAB = 0 (IER - addresses 0x4008 1004
(USART0), 0x400C 1004 (USART2), 0x400C 2004 (USART3)) bit description
Bit
Symbol
Value
Description
Reset
value
Table 827. USART Interrupt Identification Register, read only (IIR - addresses 0x4008 1008
(USART0), 0x400C 1008 (USART2), 0x400C 2008 (USART3)) bit description
Bit
Symbol
Value Description
Reset
value
0
INTSTATUS
Interrupt status.
Note that IIR[0] is active low. The pending interrupt can be
determined by evaluating IIR[3:1].
1
0
At least one interrupt is pending.
1
No interrupt is pending.
3:1
INTID
Interrupt identification.
IER[3:1] identifies an interrupt corresponding to the
USART Rx FIFO. All other combinations of IER[3:1] not
listed below are reserved (100,101,111).
0
0x3
Priority 1 (highest) - Receive Line Status (RLS).
0x2
Priority 2 - Receive Data Available (RDA).
0x6
Priority 2 - Character Time-out Indicator (CTI).
0x1
Priority 3 - THRE Interrupt.
0x0
Priority 4 (lowest) - Reserved.
5:4
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
7:6
FIFOENABLE
Copies of FCR[0].
0
8
ABEOINT
End of auto-baud interrupt.
True if auto-baud has finished successfully and interrupt is
enabled.
0
9
ABTOINT
Auto-baud time-out interrupt.
True if auto-baud has timed out and interrupt is enabled.
0
31:10 -
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA