LPC2364 datasheet(29/59 Pages) NXP

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LPC2364_65_66_67_68_6

Product data sheet

Rev. 06 — 1 February 2010

29 of 59

NXP Semiconductors

LPC2364/65/66/67/68

Single-chip 16-bit/32-bit microcontrollers

• Incorrect/Incomplete feed sequence causes reset/interrupt if enabled.

• Flag to indicate watchdog reset.

• Programmable 32-bit timer with internal prescaler.

• Selectable time period from (Tcy(WDCLK) × 256 × 4) to (Tcy(WDCLK) × 232 × 4) in

multiples of Tcy(WDCLK) × 4.

• The Watchdog Clock (WDCLK) source can be selected from the RTC clock, the

Internal RC oscillator (IRC), or the APB peripheral clock. This gives a wide range of

potential timing choices of Watchdog operation under different power reduction

conditions. It also provides the ability to run the WDT from an entirely internal source

that is not dependent on an external crystal and its associated components and

wiring, for increased reliability.

7.23 RTC and battery RAM

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

when it is off. It uses little power in Power-down and Deep power-down modes. On the

LPC2364/65/66/67/68, the RTC can be clocked by a separate 32.768 kHz oscillator, or by

a programmable prescale divider based on the APB clock. Also, the RTC is powered by its

own power supply pin, VBAT, which can be connected to a battery or to the same 3.3 V

supply used by the rest of the device.

The VBAT pin supplies power only to the RTC and the battery RAM. These two functions

require a minimum of power to operate, which can be supplied by an external battery.

7.23.1 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 32 kHz oscillator or programmable prescaler from APB clock.

• 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,

and selected fractional second values.

• 2 kB data SRAM powered by VBAT.

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

7.24 Clocking and power control

7.24.1 Crystal oscillators

The LPC2364/65/66/67/68 includes three independent oscillators. These are the Main

Oscillator, the Internal RC oscillator, and the RTC oscillator. Each oscillator can be used

for more than one purpose as required in a particular application. Any of the three clock

sources can be chosen by software to drive the PLL and ultimately the CPU.

Following reset, the LPC2364/65/66/67/68 will operate from the Internal RC oscillator until

switched by software. This allows systems to operate without any external crystal and the

bootloader code to operate at a known frequency.

LPC2364 Datasheet(PDF) 29 Page - NXP Semiconductors

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