M55800A Atmel Corporation, M55800A Datasheet - Page 75

• Manufacturer Part Number: M55800A
• Manufacturer: Atmel Corporation

Specifications of M55800A

• Flash (kbytes): 0 Kbytes
• Pin Count: 176
• Max. Operating Frequency: 33 MHz
• Cpu: ARM7TDMI
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 58
• Ext Interrupts: 58
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Uart: 3
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 72
• Resistive Touch Screen: No
• Dac Channels: 1
• Dac Resolution (bits): 10
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 8
• Self Program Memory: NO
• External Bus Interface: 1
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 3.3/5.0
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 6
• Output Compare Channels: 6
• Input Capture Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: No

13.2
13.2.1
13.2.2
13.2.3
1745F–ATARM–06-Sep-07
Functional Description
Timing
Alarm
Error Checking
The RTC provides a full Binary-Coded Decimal (BCD) clock which 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.
The RTC is updated in real-time at one second intervals in normal mode for the counters of sec-
onds, at 1 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 is
required.
The RTC has five programmable fields with which to program an alarm: MONTH and DATE in
the Calendar Alarm Register (RTC_CAR), and SEC, MIN and HOUR in the Time Alarm Register
(RTC_TAR). Each of these fields can be enabled or disabled using the bits MTHEN, DATEN,
SECEN, MINEN, HOUREN to match the alarm condition.
A verification on user interface data is performed when accessing the century, year, month,
date, day, hours, minutes, seconds and alarms. A check is performed on illegal BCD entries
such as illegal date of the month with regards to the year and century configured.
If one of the time fields is not correct, the data is not loaded into the register/counter and a flag is
set in the Valid Entry Register (RTC_VER). This flag cannot be reset by the user. It is reset as
soon as an acceptable value is programmed. This avoids any further side effects in the hard-
ware. The same processing is done for the alarm.
The following checks are processed:
• 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.
• Depending on the combination of fields enabled, a large number of possibilities are available
1. Century (check if it is in range 19 - 20)
2. Year (BCD entry check)
3. Date (check range 01 - 31)
4. Month (check if it is in BCD range 01 - 12,
5. Day (check range 1 - 7)
and an interrupt generated if enabled) at a given month, date, hour, minute and second.
to the user ranging from minutes to 365/366 days.
check validity regarding “date”)
AT91M5880A
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