ATxmega128A1 Atmel Corporation, ATxmega128A1 Datasheet - Page 296

• Manufacturer Part Number: ATxmega128A1
• Manufacturer: Atmel Corporation

Specifications of ATxmega128A1

• Flash (kbytes): 128 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 78
• Ext Interrupts: 78
• Usb Speed: No
• Usb Interface: No
• Spi: 12
• Twi (i2c): 4
• Uart: 8
• 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: 4
• Dac Resolution (bits): 12
• Temp. Sensor: Yes
• Crypto Engine: AES/DES
• Sram (kbytes): 8
• Eeprom (bytes): 2048
• Self Program Memory: YES
• External Bus Interface: 1
• Dram Memory: sdram
• 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: 8
• Output Compare Channels: 24
• Input Capture Channels: 24
• Pwm Channels: 24
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

25.7
25.8
25.9
8077H–AVR–12/09
Compare function
Starting a conversion
ADC Clock and Conversion Timing
Figure 25-11. Unsigned single ended and internal input, input range, and result representation
The ADC has a built in 12-bit compare function. The ADC compare register can hold a 12-bit
value that represent an analog threshold voltage. Each ADC Channel can be configured to auto-
matically compare its result with this 12-bit compare value to give an interrupt or event only
when the result is above or below the threshold.
All four ADC Channels share the same compare register.
Before a conversion is started, the desired input source must be selected for one or more ADC
channels. An ADC conversion for a ADC channel can either be started by the application soft-
ware writing to the start conversion bit for the ADC channel, or from any of the events in the
Event System. It is possible to write the start conversion bit for several ADC channels at the
same time, or to use one event to trigger conversions on several ADC channels at the same
time. Using this it is possible to scan several or all ADC channels from one event.
The ADC is clocked from the Peripheral Clock. The ADC can prescale the Peripheral Clock to
provide an ADC Clock (Clk
Figure 25-12. ADC Prescaler
The maximum ADC sample rate is given by the he ADC clock frequency (f
sample a new measurement on every ADC clock cycle.
The propagation delay of an ADC measurement is given by:
Sample Rate
VREF
GND
−
Δ
V
=
f
ADC
PRESCALER[2:0]
ADC
Clk
) that is within the minimum and maximum frequency for the ADC.
PER
VINN
=
VREF
2
VINP
−
Δ
9-bit ADC Prescaler
V
4095
4094
4093
Dec
203
202
201
200
...
...
0
Clk
FFD
0CB
0CA
Hex
FFF
FFE
0C9
0C8
...
ADC
0
1111 1111 1111
1111 1111 1110
1111 1111 1101
0000 1100 1011
0000 1100 1010
0000 1100 1001
0000 1100 1000
0000 0000 0000
Binary
...
0000 1111 1111 1111
0000 1111 1111 1110
0000 1111 1111 1101
0000 0000 1100 1011
0000 0000 1100 1010
0000 0000 1100 1001
0000 0000 1100 1000
0000 0000 0000 0000
16-bit result register
ADC
XMEGA A
). The ADC can
...
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