ATxmega256A3 Atmel Corporation, ATxmega256A3 Datasheet - Page 79

• Manufacturer Part Number: ATxmega256A3
• Manufacturer: Atmel Corporation

Specifications of ATxmega256A3

• 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 Speed: No
• Usb Interface: No
• 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

7.4.1.4
7.4.2
7.4.2.1
7.4.2.2
7.4.2.3
8077H–AVR–12/09
External Clock Sources
2 MHz Run-time Calibrated Internal Oscillator
0.4 - 16 MHz Crystal Oscillator
External Clock Input
32.768 kHz Crystal Oscillator
This RC oscillator provides an approximate 2 MHz clock. The oscillator employs a Digital Fre-
quency Looked Loop (DFLL) that can be enabled for automatic run-time calibration of the
oscillator. A factory-calibrated value is written to the 2 MHz DFLL Calibration Register during
reset to ensure that the oscillator is running within its specification. The calibration register can
also be written from software for manual run-time calibration of the oscillator.
The XTAL1 and XTAL2 pins can be used to drive an external oscillator, either a quartz crystal or
a ceramic resonator. XTAL1 can be used as input for an external clock signal. The TOSC1 and
TOSC2 pins is dedicated for driving a 32.768 kHz crystal oscillator.
This oscillator can operate in four different modes, optimized for different frequency ranges, all
within 0.4 - 16 MHz.
Figure 7-2.
Two capacitors, C1 and C2, may be added to match the required load capacitance for the con-
nected crystal.
To drive the device from an external clock source, XTAL1 must be driven as shown in
3 on page
Figure 7-3.
A 32.768 kHz crystal oscillator can be connected between TOSC1 and TOSC2 by enabling a
dedicated Low Frequency Oscillator input circuit. A typical connection is shown in Figure
79. In this mode, XTAL2 can be used as a general I/O pin.
Crystal Oscillator Connection
External Clock Drive Configuration
Figure 7-2
P u r p o s e
E x t e r n a l
G e n e r a l
S i g n a l
C l o c k
shows a typical connection of a crystal oscillator or resonator.
I / O
C 2
C 1
X T A L 2
X T A L 1
X T A L 2
X T A L 1
G N D
XMEGA A
Figure 7-
Figure
79