ATmega168A Atmel Corporation, ATmega168A Datasheet - Page 103

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ATmega168A

Manufacturer Part Number
ATmega168A
Description
Manufacturer
Atmel Corporation
Datasheets

Specifications of ATmega168A

Flash (kbytes)
16 Kbytes
Pin Count
32
Max. Operating Frequency
20 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
23
Ext Interrupts
24
Usb Speed
No
Usb Interface
No
Spi
2
Twi (i2c)
1
Uart
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
8
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
Yes
Crypto Engine
No
Sram (kbytes)
1
Eeprom (bytes)
512
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
3
Output Compare Channels
6
Input Capture Channels
1
Pwm Channels
6
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes

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15.7.3
8271D–AVR–05/11
Fast PWM Mode
the pin is set to output. The waveform generated will have a maximum frequency of f
f
equation:
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
As for the Normal mode of operation, the TOV0 Flag is set in the same timer clock cycle that the
counter counts from MAX to 0x00.
The fast Pulse Width Modulation or fast PWM mode (WGM02:0 = 3 or 7) provides a high fre-
quency PWM waveform generation option. The fast PWM differs from the other PWM option by
its single-slope operation. The counter counts from BOTTOM to TOP then restarts from BOT-
TOM. TOP is defined as 0xFF when WGM2:0 = 3, and OCR0A when WGM2:0 = 7. In non-
inverting Compare Output mode, the Output Compare (OC0x) is cleared on the compare match
between TCNT0 and OCR0x, and set at BOTTOM. In inverting Compare Output mode, the out-
put is set on compare match and cleared at BOTTOM. Due to the single-slope operation, the
operating frequency of the fast PWM mode can be twice as high as the phase correct PWM
mode that use dual-slope operation. This high frequency makes the fast PWM mode well suited
for power regulation, rectification, and DAC applications. High frequency allows physically small
sized external components (coils, capacitors), and therefore reduces total system cost.
In fast PWM mode, the counter is incremented until the counter value matches the TOP value.
The counter is then cleared at the following timer clock cycle. The timing diagram for the fast
PWM mode is shown in
togram for illustrating the single-slope operation. The diagram includes non-inverted and
inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent compare
matches between OCR0x and TCNT0.
Figure 15-6. Fast PWM Mode, Timing Diagram
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches TOP. If the inter-
rupt is enabled, the interrupt handler routine can be used for updating the compare value.
clk_I/O
/2 when OCR0A is set to zero (0x00). The waveform frequency is defined by the following
TCNTn
OCnx
OCnx
Period
1
ATmega48A/PA/88A/PA/168A/PA/328/P
Figure
2
15-6. The TCNT0 value is in the timing diagram shown as a his-
3
f
OCnx
=
4
------------------------------------------------- -
2 N
5
(
f
clk_I/O
1
+
OCRnx
6
)
7
OCRnx Interrupt Flag Set
OCRnx Update and
TOVn Interrupt Flag Set
(COMnx1:0 = 2)
(COMnx1:0 = 3)
OC0
103
=

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