AT91RM9200_06 Datasheet, PDF (305/689 Pages) ATMEL Corporation – ARM920T-based Microcontroller

AT91RM9200
25. Real Time Clock (RTC)
25.1 Overview
The Real-time Clock (RTC) peripheral is designed for very low power consumption.
It combines a complete time-of-day clock with alarm and a two-hundred-year Gregorian calen-
dar, complemented by a programmable periodic interrupt. The alarm and calendar registers are
accessed by a 32-bit data bus.
The time and calendar values are coded in binary-coded decimal (BCD) format. The time format
can be 24-hour mode or 12-hour mode with an AM/PM indicator.
Updating time and calendar fields and configuring the alarm fields are performed by a parallel
capture on the 32-bit data bus. An entry control is performed to avoid loading registers with
incompatible BCD format data or with an incompatible date according to the current
month/year/century.
Important features of the RTC include:
• Low Power Consumption
• Full Asynchronous Design
• Two Hundred Year Calendar
• Programmable Periodic Interrupt
• Alarm and Update Parallel Load
• Control of Alarm and Update Time/Calendar Data In
25.2 Block Diagram
Figure 25-1. RTC Block Diagram
Crystal Oscillator: SLCK
32768 Divider
Time
Date
Bus Interface
Bus Interface
Entry
Control
Interrupt
Control
RTC Interrupt
25.3 Product Dependencies
25.3.1
Power Management
The Real-time Clock is continuously clocked at 32768 Hz. The Power Management Controller
has no effect on RTC behavior.
25.3.2 Interrupt
The RTC Interrupt is connected to interrupt source 1 (IRQ1) of the advanced interrupt controller.
This interrupt line is due to the OR-wiring of the system peripheral interrupt lines (System Timer,
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