ATxmega256A3BU Atmel Corporation, ATxmega256A3BU Datasheet - Page 170

• 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

8331A–AVR–07/11
Figure 14-7. Changing the period without buffering.
A counter wraparound can occur in any mode of operation when up-counting without buffering,
as shown in
and if a new TOP value that is lower than current CNT is written to PER, it will wrap before a
compare match happen.
Figure 14-8. Unbuffered dual-slope operation.
When double buffering is used, the buffer can be written at any time and still maintain correct
operation. The period register is always updated on the UPDATE condition, as shown for dual-
slope operation in
Figure 14-9. Changing the period using buffering.
CNT
CNT
CNT
BOTTOM
BOTTOM
MAX
MAX
Figure
BOTTOM
MAX
Figure
14-8. This due to the fact that CNT and PER are continuously compared,
PERBUF that is higher
New TOP written to
New Period written to
PER that is higher
than current CNT
than current CNT
14-9. This prevents wraparound and the generation of odd waveforms.
New TOP written to
PER that is higher
than current CNT
Counter Wraparound
New Period written to
PERBUF that is lower
New TOP written to
than current CNT
PER that is lower
than current CNT
Counter Wraparound
Atmel AVR XMEGA AU
New TOP written to
PER that is lower
than current CNT
New PER is updated
with PERBUF value.
"update"
"write"
"update"
"write"
"update"
"write"
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