LPC2292 datasheet(23/53 Pages) NXP

23 / 53 page

LPC2292_2294_7

Product data sheet

Rev. 7 — 4 December 2008

23 of 53

NXP Semiconductors

LPC2292/LPC2294

16/32-bit ARM microcontrollers with external memory interface

6.15.2 Features available in LPC2292/LPC2294/01 only

The LPC2292/LPC2294/01 can count external events on one of the capture inputs if the

external pulse lasts at least one half of the period of the PCLK. In this conﬁguration,

unused capture lines can be selected as regular timer capture inputs, or used as external

interrupts.

• Timer can count cycles of either the peripheral clock (PCLK) or an externally supplied

clock.

• When counting cycles of an externally supplied clock, only one of the timer’s capture

inputs can be selected as the timer’s clock. The rate of such a clock is limited to

PCLK / 4. Duration of HIGH/LOW levels on the selected CAP input cannot be shorter

than 1 / (2PCLK).

6.16 Watchdog timer

The purpose of the watchdog is to reset the microcontroller within a reasonable amount of

time if it enters an erroneous state. When enabled, the watchdog will generate a system

reset if the user program fails to ‘feed’ (or reload) the watchdog within a predetermined

amount of time.

6.16.1 Features

• Internally resets chip if not periodically reloaded.

• Debug mode.

• Enabled by software but requires a hardware reset or a watchdog reset/interrupt to be

disabled.

• Incorrect/incomplete feed sequence causes reset/interrupt if enabled.

• Flag to indicate watchdog reset.

• Programmable 32-bit timer with internal prescaler.

• Selectable time period from (Tcy(PCLK) × 256 × 4) to (Tcy(PCLK) × 232 × 4) in multiples of

Tcy(PCLK) × 4.

6.17 Real-time clock

The Real-Time Clock (RTC) is designed to provide a set of counters to measure time

when normal or idle operating mode is selected. The RTC has been designed to use little

power, making it suitable for battery powered systems where the CPU is not running

continuously (Idle mode).

6.17.1 Features

• Measures the passage of time to maintain a calendar and clock.

• Ultra-low power design to support battery powered systems.

• Provides Seconds, Minutes, Hours, Day of Month, Month, Year, Day of Week, and Day

of Year.

• Programmable Reference Clock Divider allows adjustment of the RTC to match

various crystal frequencies.

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