LPC4350 datasheet(85/145 Pages) NXP

85 / 145 page

LPC4350_30_20_10

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Objective data sheet

Rev. 2.1 — 23 September 2011

85 of 145

NXP Semiconductors

LPC4350/30/20/10

32-bit ARM Cortex-M4/M0 microcontroller

7.21 Peripherals in the RTC power domain

7.21.1 RTC

The Real Time Clock (RTC) is a set of counters for measuring time when system power is

on, and optionally when it is off. It uses very little power when its registers are not being

accessed by the CPU, especially reduced power modes. The RTC is clocked by a

separate 32 kHz oscillator that produces a 1 Hz internal time reference. The RTC is

7.21.1.1

Features

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

minutes, hours, day of month, month, year, day of week, and day of year.

• Ultra-low power design to support battery powered systems. Less than <tbd> required

for battery operation. Uses power from the CPU power supply when it is present.

• Dedicated battery power supply pin.

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

• Calibration counter allows adjustment to better than 1 sec/day with 1 sec resolution.

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

• Alarm interrupt can be generated for a specific date/time.

7.21.2 Alarm timer

The alarm timer is a 16-bit timer and counts down at 1 kHz from a preset value generating

alarms in intervals of up to 1 min. The counter triggers a status bit when it reaches 0x00

and asserts an interrupt if enabled.

The alarm timer is part of the RTC power domain and can be battery powered.

7.22 System control

7.22.1 Configuration registers (CREG)

The following settings are controlled in the configuration register block:

• BOD trip settings

• Oscillator output

• DMA-to-peripheral muxing

• Ethernet mode

• Memory mapping

• Timer/USART inputs

• Enabling the USB controllers

In addition, the CREG block contains the part identification and part configuration

information.

7.22.2 System Control Unit (SCU)

The system control unit determines the function and electrical mode of the digital pins and

allows switching between analog and digital modes of pads that are capable of both

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