Datasheet

Product data sheet Rev. 6.4 — 18 August 2014 79 of 150

NXP Semiconductors

LPC1850/30/20/10

32-bit ARM Cortex-M3 microcontroller

7.17.1.1 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. 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.

7.17.2 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.

7.18 System control

7.18.1 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.

7.18.2 System Control Unit (SCU)

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

default function 0 is selected for all pins with pull-up enabled. For pins that support a

digital and analog function, the ADC function select registers in the SCU enable the

analog function.

A separate set of analog I/Os for the ADCs and the DAC as well as most USB pins are

located on separate pads and are not controlled through the SCU.

In addition, the clock delay register for the SDRAM EMC_CLK pins and the registers that

select the pin interrupts are located in the SCU.