LPC4088 datasheet(59/123 Pages) NXP

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LPC408X_7X

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Objective data sheet

Rev. 1 — 17 September 2012

59 of 123

NXP Semiconductors

LPC408x/7x

32-bit ARM Cortex-M4 microcontroller

7.34 RTC and backup registers

The RTC is a set of counters for measuring time when system power is on, and optionally

when it is off. The RTC on the LPC408x/7x is designed to have extremely low power

consumption, i.e. less than 1

A. The RTC will typically run from the main chip power

supply conserving battery power while the rest of the device is powered up. When

operating from a battery, the RTC will continue working down to 2.1 V. Battery power can

be provided from a standard 3 V lithium button cell.

An ultra-low power 32 kHz oscillator will provide a 1 Hz clock to the time counting portion

of the RTC, moving most of the power consumption out of the time counting function.

The RTC includes a calibration mechanism to allow fine-tuning the count rate in a way

that will provide less than 1 second per day error when operated at a constant voltage and

temperature.

The RTC contains a small set of backup registers (20 bytes) for holding data while the

main part of the LPC408x/7x is powered off.

The RTC includes an alarm function that can wake up the LPC408x/7x from all reduced

power modes with a time resolution of 1 s.

7.34.1 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.

• Dedicated power supply pin can be connected to a battery or to the main 3.3 V.

• Periodic interrupts can be generated from increments of any field of the time registers.

• Backup registers (20 bytes) powered by VBAT.

• RTC power supply is isolated from the rest of the chip.

7.35 Event monitor/recorder

The event monitor/recorder allows recording of tampering events in sealed product

enclosures. Sensors report any attempt to open the enclosure, or to tamper with the

device in any other way. The event monitor/recorder stores records of such events when

the device is powered only by the backup battery.

7.35.1 Features

• Supports three digital event inputs in the VBAT power domain.

• An event is defined as a level change at the digital event inputs.

• For each event channel, two timestamps mark the first and the last occurrence of an

event. Each channel also has a dedicated counter tracking the total number of events.

Timestamp values are taken from the RTC.

• Runs in VBAT power domain, independent of system power supply. The

event/recorder/monitor can therefore operate in Deep power-down mode.

• Very low power consumption.

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