LPC2141_42_44_46_48 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 5 — 12 August 2011 20 of 45
NXP Semiconductors
LPC2141/42/44/46/48
Single-chip 16-bit/32-bit microcontrollers
– Stop timer on match with optional interrupt generation.
– Reset timer on match with optional interrupt generation.
• Four external outputs per timer/counter corresponding to match registers, with the
following capabilities:
– Set LOW on match.
– Set HIGH on match.
– Toggle on match.
– Do nothing on match.
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 pre-scaler.
• Selectable time period from (T
cy(PCLK)
256 4) to (T
cy(PCLK)
2
32
4) in multiples of
T
cy(PCLK)
4.
6.17 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).
6.17.1 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.
• Can use either the RTC dedicated 32 kHz oscillator input or clock derived from the
external crystal/oscillator input at XTAL1. Programmable reference clock divider
allows fine adjustment of the RTC.
• Dedicated power supply pin can be connected to a battery or the main 3.3 V.
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