AT91SAM9G45-EKES Atmel, AT91SAM9G45-EKES Datasheet - Page 94

• Manufacturer Part Number: AT91SAM9G45-EKES
• Description: KIT EVAL FOR AT91SAM9G45
• Manufacturer: Atmel
• Series: AT91SAM Smart ARMr
• Type: MCUr

Specifications of AT91SAM9G45-EKES

• Contents: Board
• Processor To Be Evaluated: SAM9G45
• Data Bus Width: 32 bit
• Interface Type: I2C, SPI, UART
• Maximum Operating Temperature: + 50 C
• Minimum Operating Temperature: - 10 C
• Operating Supply Voltage: 1.8 V to 3.3 V
• For Use With/related Products: AT91SAM9G45
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: Q4626953

14.4
14.4.1
14.4.2
14.5
14.5.1
14.5.2
14.5.3
94
Product Dependencies
Functional Description
AT91SAM9G45
Power Management
Interrupt
Reference Clock
Timing
Alarm
The Real-time Clock is continuously clocked at 32768 Hz. The Power Management Controller
has no effect on RTC behavior.
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,
Real Time Clock, Power Management Controller, Memory Controller, etc.). When a system
interrupt occurs, the service routine must first determine the cause of the interrupt. This is done
by reading the status registers of the above system peripherals successively.
The RTC provides a full binary-coded decimal (BCD) clock that includes century (19/20), year
(with leap years), month, date, day, hours, minutes and seconds.
The valid year range is 1900 to 2099, a two-hundred-year Gregorian calendar achieving full Y2K
compliance.
The RTC can operate in 24-hour mode or in 12-hour mode with an AM/PM indicator.
Corrections for leap years are included (all years divisible by 4 being leap years, including year
2000). This is correct up to the year 2099.
After hardware reset, the calendar is initialized to Thursday, January 1, 1998.
The reference clock is Slow Clock (SLCK). It can be driven internally or by an external 32.768
kHz crystal.
During low power modes of the processor (idle mode), the oscillator runs and power consump-
tion is critical. The crystal selection has to take into account the current consumption for power
saving and the frequency drift due to temperature effect on the circuit for time accuracy.
The RTC is updated in real time at one-second intervals in normal mode for the counters of sec-
onds, at one-minute intervals for the counter of minutes and so on.
Due to the asynchronous operation of the RTC with respect to the rest of the chip, to be certain
that the value read in the RTC registers (century, year, month, date, day, hours, minutes, sec-
onds) are valid and stable, it is necessary to read these registers twice. If the data is the same
both times, then it is valid. Therefore, a minimum of two and a maximum of three accesses are
required.
The RTC has five programmable fields: month, date, hours, minutes and seconds.
Each of these fields can be enabled or disabled to match the alarm condition:
• If all the fields are enabled, an alarm flag is generated (the corresponding flag is asserted
• If only the “seconds” field is enabled, then an alarm is generated every minute.
and an interrupt generated if enabled) at a given month, date, hour/minute/second.
6438F–ATARM–21-Jun-10