ATxmega256A3U Atmel Corporation, ATxmega256A3U Datasheet - Page 19

• Manufacturer Part Number: ATxmega256A3U
• Manufacturer: Atmel Corporation

Specifications of ATxmega256A3U

• 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: 50
• Ext Interrupts: 50
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 10
• Twi (i2c): 2
• Uart: 7
• 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
10.3.1
10.3.2
8386A–AVR–07/11
Clock Options
32kHz Ultra Low Power Internal Oscillator
32.768kHz Calibrated Internal Oscillator
Figure 10-1. The Clock system, clock sources and clock distribution
This oscillator provides an approximate 32kHz clock. The 32kHz Ultra Low Power (ULP) Internal
Oscillator is a very low power clock source, and it is not designed for high accuracy. The oscilla-
tor employs a built in prescaler providing a 1kHz output. The oscillator is automatically
enabled/disabled when used as clock source for any part of the device. This oscillator can be
selected as clock source for the RTC.
This oscillator provides an approximate 32.768kHz clock. A factory-calibrated value is written to
the 32.768kHz oscillator calibration register during reset to ensure that the oscillator is running-
within its specification. The calibration register can also be written from software for run-time
calibration of the oscillator frequency. The oscillator employs a built in prescaler providing both a
32.768kHz output and a 1.024kHz output.
Brown-out
Detector
Int. ULP
32 kHz
Watchdog
Timer
Real Time
Counter
32.768 kHz
Int. OSC
RTCSRC
clk
RTC
Peripherals
32.768 kHz
TOSC
clk
PER4
clk
XOSCSEL
PER2
clk
PER
0.4 – 16 MHz
System Clock Prescalers
System Clock Multiplexer
XTAL
RAM
clk
(SCLKSEL)
SYS
32 MHz
Int. Osc
PLLSRC
PLL
AVR CPU
XMEGA A3U
Int. Osc
2 MHz
Non-Volatile
clk
Memory
Prescaler
CPU
USBSRC
USB
clk
USB
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