ATxmega256A3 Atmel Corporation, ATxmega256A3 Datasheet - Page 69

• 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

6.5
6.6
6.7
6.7.1
8077H–AVR–12/09
Event Timing
Filtering
Quadrature Decoder
Quadrature Operation
An event normally lasts for one peripheral clock cycle, but some event sources, such as low
level on an I/O pin, will generate events continuously. Details on this are described in the
datasheet for each peripheral, but unless stated, an event lasts for one peripheral clock cycle
only.
It takes maximum two clock cycles from an event is generated until the event actions in other
peripherals is triggered. It takes one clock cycle from the event happens until it is registered by
the event routing network on the first positive clock edge. It takes an additional clock cycle to
route the event through the event channel to the event user.
Each event channel includes a digital filter. When this is enabled for an event channel, an event
must be sampled with the same value for configurable number of system clock cycles before it is
accepted. This is primarily intended for pin change events.
The Event System includes three Quadrature Decoders (QDECs). This enables the Event Sys-
tem to decode quadrature input on I/O pins, and send data events that a Timer/Counter can
decode to trigger the appropriate event action: count up, count down or index/reset.
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decoded, and how they can be generated. The QDECs and related features, control and status
register are available for event channel 0, 2 and 4.
Table 6-2.
A quadrature signal is characterized by having two square waves phase shifted 90 degrees rela-
tive to each other. Rotational movement can be measured by counting the edges of the two
waveforms. The phase relationship between the two square waves determines the direction of
rotation.
STROBE
0
0
1
1
summarizes which quadrature decoder data events are available, how they are
DATA
Quadrature Decoder Data Events
0
1
0
1
Data Event User
No Event
Index/Reset
Count Down
Count Up
Signaling Event User
No Event
Signaling Event
Signaling Event
No Event
XMEGA A
Table 6-2
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