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UM10601
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
84 of 313
NXP Semiconductors
UM10601
Chapter 8: LPC800 Pin interrupts/pattern match engine
8.5.1 Pin interrupts
From all available GPIO pins, up to eight pins can be selected in the system control block
to serve as external interrupt pins (see
). The external interrupt pins are
connected to eight individual interrupts in the NVIC and are created based on rising or
falling edges or on the input level on the pin.
8.5.2 Pattern match engine
The pattern match feature allows complex boolean expressions to be constructed from
the same set of eight GPIO pins that were selected for the GPIO pin interrupts. The
pattern match logic continuously monitors these eight inputs and generates interrupts
when any one or more minterms (product terms) of the specified boolean expression is
matched. A separate interrupt request is generated for each individual minterm.
In addition, the pattern match module can be enabled to generate a Receive Event
(RXEV) output to the ARM core when the entire boolean expression is true (i.e. when any
minterm is matched).
The RXEV output is also be routed to GPIO_INT_BMAT pin. This allows the GPIO module
to provide a rudimentary programmable logic capability employing up to eight inputs and
one output.
The pattern match function utilizes the same eight interrupt request lines as the pin
interrupts so these two features are mutually exclusive as far as interrupt generation is
concerned. A control bit is provided to select whether interrupt requests are generated in
response to the standard pin interrupts or to pattern matches. Note that, if the pin
interrupts are selected, the RXEV request to the CPU can still be enabled for pattern
matches.
Remark:
Pattern matching cannot be used to wake the part up from power-down modes.
Pin interrupts must be selected in order to use the GPIO for wake-up.
The pattern match module is constructed of eight bit-slice elements. Each bit slice is
programmed to represent one component of one minterm (product term) within the
boolean expression. The interrupt request associated with the last bit slice for a particular
minterm will be asserted whenever that minterm is matched.
(See bit slice drawing
).
The pattern match capability can be used to create complex software state machines.
Each minterm (and its corresponding individual interrupt) represents a different transition
event to a new state. Software can then establish the new set of conditions (i.e new
boolean expression) that will cause a transition out of the current state.