ATxmega256A3BU Atmel Corporation, ATxmega256A3BU Datasheet - Page 121

• Manufacturer Part Number: ATxmega256A3BU
• Manufacturer: Atmel Corporation

Specifications of ATxmega256A3BU

• Flash (kbytes): 256 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 47
• Ext Interrupts: 49
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 8
• Twi (i2c): 2
• Uart: 6
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 16
• Adc Resolution (bits): 12
• Adc Speed (ksps): 2000
• Analog Comparators: 4
• Resistive Touch Screen: No
• Dac Channels: 2
• Dac Resolution (bits): 12
• Temp. Sensor: Yes
• Crypto Engine: AES/DES
• Sram (kbytes): 16
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.6 to 3.6
• Operating Voltage (vcc): 1.6 to 3.6
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 7
• Output Compare Channels: 22
• Input Capture Channels: 22
• Pwm Channels: 22
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

10.3.3
10.3.4
10.3.5
10.4
10.5
10.5.1
8331A–AVR–07/11
Configuration
Operation
Crystal Oscillator with Failure Monitor
32-bit Real-time Counter
Backup Registers
Main Power Loss
The crystal oscillator (XOSC) supports connection of a external 32.768kHz crystal. It provides a
prescaled clock output selectable to 1.024kHz or 1Hz. The crystal oscillator is designed for ultra
low power consumption and by default is configured for low ESR and load capacitance crystals.
It is possible to enable a high ESR mode to drive crystals with high ESR or load capacitance, but
this will increase current consumption. The crystal oscillator failure monitor will detect if the crys-
tal is permanently or temporarily stopped and then set the crystal oscillator failure flag.
The 32-bit real-time counter (RTC) will count each clock output from the crystal oscillator. It pro-
vides a one-millisecond or one-second resolution, depending on the crystal oscillator clock
output selection. For more details on the 32-bit RTC, refer to the
Counter” on page
The two backup registers can be used to store volatile data parameters when Vcc is not present.
During device initialization, the battery backup system and RTC must be configured before they
can be used. The recommended configuration sequence is:
The main BOD monitors the main voltage (Vcc) level and controls the power switching. This
must always be enabled. In active and idle modes, the BOD must be in continuos mode. In deep
sleep modes, the BOD can be in continuos or sampled mode. The system is designed as a
power backup system for the RTC. Reset sources other than the BOD and power loss (i.e. exter-
nal reset, watchdog reset, and software reset) must be treated as a system reset. In this case,
the device state should be treated as unknown and lead to complete reinitialisation, including
battery backup system configuration.
When Vcc drops below the programmed BOD threshold voltage, the device will:
The battery backup system will continue to run as normal during the power switch and after-
wards. When main power is lost, it is not possible to access or read the status from the registers.
1. Apply a reset
2. Set the access enable bit
3. Optionally configure the oscillator output and ESR selection
4. Optionally enable the crystal oscillator failure monitor and the required delay before
5. Enable the crystal oscillator
6. Wait until the crystal oscillator ready flag is set
7. Configure and enable the RTC
1. Switch the battery backup system to be powered from the V
2. Ignore any input signals to the system to prevent accidental or partial configuration.
3. Stretch the 1Hz / 1.024kHz clock signal to avoid a clock edge when switching is active.
4. Reset the part of the device not powered from the V
continuing configuration
BBBOD.
223.
Atmel AVR XMEGA AU
BAT
pin.
BAT
”RTC32 - 32-bit Real-Time
pin and enable the
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