ATxmega256A3U Atmel Corporation, ATxmega256A3U Datasheet - Page 223

• 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

19. RTC32 - 32-bit Real-Time Counter
19.1
19.2
19.2.1
8331A–AVR–07/11
Features
Overview
Clock selection
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The 32-bit real-time counter (RTC32) is a 32-bit counter that typically runs continuously, includ-
ing in low-power sleep modes, to keep track of time. It can wake up the device from sleep modes
and/or interrupt the device at regular intervals.
The reference clock is typically a 1Hz prescaled output from a high-accuracy crystal of
32.768kHz, a configuration optimized for low power consumption and 1s resolution. The faster
1.024kHz output can be selected if the timer needs 1ms resolution.
The RTC32 will give a compare interrupt and/or event when the counter equals the compare
register value, and a overflow interrupt and/or event when it equals the period register value.
Figure 19-1. 32-bit real-time counter overview
An external 32.768kHz crystal oscillator must be used as the clock source. Two different fre-
quency outputs are available from this, and the RTC32 clock input can be 1.024kHz or 1Hz.
32-bit resolution
32.768kHz external crystal clock source with selectable prescaling
One compare register
One period register
Clear counter on period overflow
Optional interrupt/ event on overflow and compare match
– 1.024kHz
– 1Hz
1.024kHz
1Hz
Atmel AVR XMEGA AU
32-bit Compare
32-bit Counter
=
=
32-bit Period
Overflow
Compare Match
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