ATMEGA329P-20MN Atmel, ATMEGA329P-20MN Datasheet - Page 147

• Manufacturer Part Number: ATMEGA329P-20MN
• Description: IC MCU AVR 32K 20MHZ 64QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA329P-20MN

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 54
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-MLF®, 64-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

17.7.3
8021G–AVR–03/11
Fast PWM Mode
The timing diagram for the CTC mode is shown in
increases until a compare match occurs between TCNT2 and OCR2A, and then counter
(TCNT2) is cleared.
Figure 17-5. CTC Mode, Timing Diagram
An interrupt can be generated each time the counter value reaches the TOP value by using the
OCF2A Flag. If the interrupt is enabled, the interrupt handler routine can be used for updating
the TOP value. However, changing the TOP to a value close to BOTTOM when the counter is
running with none or a low prescaler value must be done with care since the CTC mode does
not have the double buffering feature. If the new value written to OCR2A is lower than the cur-
rent value of TCNT2, the counter will miss the compare match. The counter will then have to
count to its maximum value (0xFF) and wrap around starting at 0x00 before the compare match
can occur.
For generating a waveform output in CTC mode, the OC2A output can be set to toggle its logical
level on each compare match by setting the Compare Output mode bits to toggle mode
(COM2A1:0 = 1). The OC2A value will not be visible on the port pin unless the data direction for
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, 32, 64, 128, 256, or 1024).
As for the Normal mode of operation, the
counter counts from MAX to 0x00.
The fast Pulse Width Modulation or fast PWM mode (WGM21:0 = 3) provides a high frequency
PWM waveform generation option. The fast PWM differs from the other PWM option by its sin-
gle-slope operation. The counter counts from BOTTOM to MAX then restarts from BOTTOM. In
non-inverting Compare Output mode, the Output Compare (OC2A) is cleared on the compare
match between TCNT2 and OCR2A, and set at BOTTOM. In inverting Compare Output mode,
the output 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 uses dual-slope operation. This high frequency makes the fast PWM mode well suited
clk_I/O
/2 when OCR2A is set to zero (0x00). The waveform frequency is defined by the following
TCNTn
OCnx
(Toggle)
Period
1
f
OCnx
2
=
TOV2
------------------------------------------------- -
2 N
3
⋅
Flag is set in the same timer clock cycle that the
⋅
f
(
clk_I/O
1
+
Figure
4
OCRnx
ATmega329P/3290P
17-5. The counter value (TCNT2)
)
OCnx Interrupt Flag Set
(COMnx1:0 = 1)
OC2A
147
=