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18.1 Features
18.2 Description
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 little power in Power-down mode. On the
LPC2131/2/4/6/8, the RTC can be clocked by a separate 32.768 KHz oscillator, or by a
programmable prescale divider based on the VPB clock. Also, the RTC is powered by its
own power supply pin, V
supply used by the rest of the device.
18.3 Architecture
User manual
UM10120
Chapter 18: Real Time Clock
Rev. 01 — 24 June 2005
•
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 VPB clock.
•
Dedicated power supply pin can be connected to a battery or to the main 3.3 V.
BAT
CLOCK GENERATOR
CLK1
CCLK
TIME
COUNTERS
COUNTER INCREMENT
Counter
INTERRUPT ENABLE
enables
Fig 51. RTC block diagram
Rev. 01 — 24 June 2005
, which can be connected to a battery or to the same 3.3 V
CLK32k
MUX
Strobe
COMPARATORS
INTERRUPT GENERATOR
User manual
RTC OSCILLATOR
REFERENCE CLOCK
DIVIDER (PRESCALER)
ALARM
REGISTERS
ALARM MASK
REGISTER
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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