LPC2124FBD64SLASH01 datasheet(18/40 Pages) NXP

18 / 40 page

LPC2114_2124_6

Product data sheet

Rev. 06 — 10 December 2007

18 of 40

NXP Semiconductors

LPC2114/2124

Single-chip 16/32-bit microcontrollers

6.13.2 Features available in LPC2114/2124/01 only

• 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 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 can not be shorter

than 1 / (2PCLK).

6.14 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.

6.14.1 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 pre-scaler.

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

Tcy(PCLK) × 4.

6.15 Real-time clock

The 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).

6.15.1 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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