© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
User manual
Rev. 01 — 15 August 2005
275
19.1 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 VPB clock.
•
Dedicated power supply pin can be connected to a battery or to the main 3.3 V.
19.2 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
LPC2141/2/4/6/8, 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
BAT
, which can be connected to a battery or to the same 3.3 V
supply used by the rest of the device.
19.3 Architecture
UM10139
Chapter 19: Real Time Clock
Rev. 01 — 15 August 2005
User manual
Fig 61. RTC block diagram
CCLK
INTERRUPT GENERATOR
COUNTER INCREMENT
INTERRUPT ENABLE
ALARM MASK
REGISTER
Counter
enables
CLK1
REFERENCE CLOCK
DIVIDER (PRESCALER)
CLK32k
Strobe
COMPARATORS
CLOCK GENERATOR
ALARM
REGISTERS
TIME
COUNTERS
RTC OSCILLATOR
MUX