NXP Semiconductors LPC1768 - UART1 Interrupt Identification Register (U1 IIR - 0 X4001 0008)

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User manual Rev. 3 — 19 December 2013 324 of 841
NXP Semiconductors
UM10360
Chapter 15: LPC176x/5x UART1
15.4.5 UART1 Interrupt Identification Register (U1IIR - 0x4001 0008)
The U1IIR provides a status code that denotes the priority and source of a pending
interrupt. The interrupts are frozen during an U1IIR access. If an interrupt occurs during
an U1IIR access, the interrupt is recorded for the next U1IIR access.
Bit U1IIR[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.
If the IntStatus bit is 1 no interrupt is pending and the IntId bits will be zero. If the IntStatus
is 0, a non auto-baud interrupt is pending in which case the IntId bits identify the type of
interrupt and handling as described in Table 296
. Given the status of U1IIR[3:0], an
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 294: UART1 Interrupt Enable Register (U1IER - address 0x4001 0004 when DLAB = 0) bit description …continued
Bit Symbol Value Description Reset
Value
Table 295: UART1 Interrupt Identification Register (U1IIR - address 0x4001 0008) bit description
Bit Symbol Value Description Reset
Value
0 IntStatus Interrupt status. Note that U1IIR[0] is active low. The pending interrupt can be
determined by evaluating U1IIR[3:1].
1
0 At least one interrupt is pending.
1 No interrupt is pending.
3:1 IntId Interrupt identification. U1IER[3:1] identifies an interrupt corresponding to the UART1
Rx or TX FIFO. All other combinations of U1IER[3:1] not listed below are reserved
(100,101,111).
0
011 1 - Receive Line Status (RLS).
010 2a - Receive Data Available (RDA).
110 2b - Character Time-out Indicator (CTI).
001 3 - THRE Interrupt.
000 4 - Modem Interrupt.
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 FIFO Enable Copies of U1FCR[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, the value read from a reserved bit is not defined. NA