UM10462
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User manual
Rev. 5.5 — 21 December 2016
246 of 523
NXP Semiconductors
UM10462
Chapter 12: LPC11U3x/2x/1x USART
12.5.5 USART Interrupt Identification Register (Read Only)
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.
7:4
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
8
ABEOINTEN
Enables the end of auto-baud interrupt.
0
0
Disable end of auto-baud Interrupt.
1
Enable end of auto-baud Interrupt.
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 234. USART Interrupt Enable Register when DLAB = 0 (IER - address 0x4000 8004) bit
description
…continued
Bit
Symbol
Value
Description
Reset
value
Table 235. USART Interrupt Identification Register Read only (IIR - address 0x4004 8008) 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 values of
IER[3:1] not listed below are reserved.
0
0x3
1 - Receive Line Status (RLS).
0x2
2a - Receive Data Available (RDA).
0x6
2b - Character Time-out Indicator (CTI).
0x1
3 - THRE Interrupt.
0x0
4 - Modem status
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
FIFOEN
These bits are equivalent to 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