LPC11U2X datasheet(21/67 Pages) PHILIPS

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LPC11U2X

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Preliminary data sheet

Rev. 1 — 29 November 2011

21 of 67

NXP Semiconductors

LPC11U2x

32-bit ARM Cortex-M0 microcontroller

• Four match registers per timer that allow:

– Continuous operation with optional interrupt generation on match.

– Stop timer on match with optional interrupt generation.

– Reset timer on match with optional interrupt generation.

• Up to four external outputs corresponding to match registers, with the following

capabilities:

– Set LOW on match.

– Set HIGH on match.

– Toggle on match.

– Do nothing on match.

• The timer and prescaler can be configured to be cleared on a designated capture

event. This feature permits easy pulse-width measurement by clearing the timer on

the leading edge of an input pulse and capturing the timer value on the trailing edge.

7.15 System tick timer

The ARM Cortex-M0 includes a system tick timer (SYSTICK) that is intended to generate

a dedicated SYSTICK exception at a fixed time interval (typically 10 ms).

7.16 Windowed WatchDog Timer (WWDT)

The purpose of the WWDT is to prevent an unresponsive system state. If software fails to

update the watchdog within a programmable time window, the watchdog resets the

microcontroller

7.16.1 Features

• Internally resets chip if not periodically reloaded during the programmable time-out

period.

• Optional windowed operation requires reload to occur between a minimum and

maximum time period, both programmable.

• Optional warning interrupt can be generated at a programmable time before watchdog

time-out.

• Software enables the WWDT, but a hardware reset or a watchdog reset/interrupt is

required to disable the WWDT.

• Incorrect feed sequence causes reset or interrupt, if enabled.

• Flag to indicate watchdog reset.

• Programmable 24-bit timer with internal prescaler.

• Selectable time period from (Tcy(WDCLK)  256  4) to (Tcy(WDCLK)  224  4) in

multiples of Tcy(WDCLK)  4.

• The Watchdog Clock (WDCLK) source can be selected from the IRC or the dedicated

watchdog oscillator (WDO). The clock source selection provides a wide range of

potential timing choices of watchdog operation under different power conditions.

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