UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
926 of 1269
35.1 How to read this chapter
The RTC is available on all LPC43xx parts.
35.2 Basic configuration
The RTC is configured as follows:
•
See
for clocking and power control. The 1 kHz output of the 32 kHz
oscillator must be enabled in the CREG0 register in the CREG block (see
).
•
The RTC interrupt is connected to slot # 5 in the Event router slot #47 in the NVIC.
•
The functionality of the RTC_ALARM pin is controlled by the CREG0 register (see
). By default, the RTC Alarm interrupt can be monitored on this pin.
Remark:
After initializing the 32 kHz oscillator, wait for 2 sec before writing to the RTC
registers.
35.3 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
and selected fractional second values.
•
An Alarm interrupt can be generated for a specific date/time.
UM10503
Chapter 35: LPC43xx Real-Time Clock (RTC)
Rev. 1.3 — 6 July 2012
User manual
Table 780. RTC clocking and power control
Base clock
Branch clock Operating frequency
Clock to the RTC register
interface
BASE_M4_CLK
CLK_M4_BUS up to 204 MHz
32 kHz crystal oscillator output
for the RTC counter/timer clock
-
-
1024 Hz (fixed frequency);
the RTC receives an
internal 1 Hz clock.