p89lpc9171fdh NXP Semiconductors, p89lpc9171fdh Datasheet - Page 42

• Manufacturer Part Number: p89lpc9171fdh
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core, 2 Kb 3 V Byte-erasable Flash With 8-bit Adc
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89LPC9151_61_71_2
Product data sheet
7.14.1 External interrupt inputs
Each interrupt source can be individually programmed to one of four priority levels by
setting or clearing bits in the interrupt priority registers IP0, IP0H, IP1 and IP1H. An
interrupt service routine in progress can be interrupted by a higher priority interrupt, but
not by another interrupt of the same or lower priority. The highest priority interrupt service
cannot be interrupted by any other interrupt source. If two requests of different priority
levels are pending at the start of an instruction, the request of higher priority level is
serviced.
If requests of the same priority level are pending at the start of an instruction, an internal
polling sequence determines which request is serviced. This is called the arbitration
ranking. Note that the arbitration ranking is only used to resolve pending requests of the
same priority level.
The P89LPC9151 and P89LPC9171 have two external interrupt inputs as well as the
Keypad Interrupt function. The P89LPC9161 has one external interrupt input as well as
the Keypad Interrupt function These external interrupt inputs are identical to those present
on the standard 80C51 microcontrollers.
These external interrupts can be programmed to be level-triggered or edge-triggered by
setting or clearing bit IT1 or IT0 in Register TCON.
In edge-triggered mode, if successive samples of the INTn pin show a HIGH in one cycle
and a LOW in the next cycle, the interrupt request flag IEn in TCON is set, causing an
interrupt request.
If an external interrupt is enabled when the P89LPC9151/9161/9171 is put into
Power-down or Idle mode, the interrupt will cause the processor to wake-up and resume
operation. Refer to
Section 7.17 “Power reduction modes”
Rev. 02 — 9 February 2010
P89LPC9151/9161/9171
8-bit microcontroller with 8-bit ADC
for details.
© NXP B.V. 2010. All rights reserved.
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