ATMEGA329P-20MN Atmel, ATMEGA329P-20MN Datasheet - Page 145

• 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

17.5.3
17.6
8021G–AVR–03/11
Compare Match Output Unit
Using the Output Compare Unit
Since writing TCNT2 in any mode of operation will block all compare matches for one timer clock
cycle, there are risks involved when changing TCNT2 when using the Output Compare unit,
independently of whether the Timer/Counter is running or not. If the value written to TCNT2
equals the OCR2A value, the compare match will be missed, resulting in incorrect waveform
generation. Similarly, do not write the TCNT2 value equal to BOTTOM when the counter is
counting down.
The setup of the OC2A should be performed before setting the Data Direction Register for the
port pin to output. The easiest way of setting the OC2A value is to use the Force Output Com-
pare (FOC2A) strobe bit in Normal mode. The OC2A Register keeps its value even when
changing between Waveform Generation modes.
Be aware that the COM2A1:0 bits are not double buffered together with the compare value.
Changing the COM2A1:0 bits will take effect immediately.
The Compare Output mode (COM2A1:0) bits have two functions. The Waveform Generator
uses the COM2A1:0 bits for defining the Output Compare (OC2A) state at the next compare
match. Also, the COM2A1:0 bits control the OC2A pin output source.
plified schematic of the logic affected by the COM2A1:0 bit setting. The I/O Registers, I/O bits,
and I/O pins in the figure are shown in bold. Only the parts of the general I/O Port Control Regis-
ters (DDR and PORT) that are affected by the COM2A1:0 bits are shown. When referring to the
OC2A state, the reference is for the internal OC2A Register, not the OC2A pin.
Figure 17-4. Compare Match Output Unit, Schematic
The general I/O port function is overridden by the Output Compare (OC2A) from the Waveform
Generator if either of the COM2A1:0 bits are set. However, the OC2A pin direction (input or out-
put) is still controlled by the Data Direction Register (DDR) for the port pin. The Data Direction
COMnx1
COMnx0
FOCnx
clk
I/O
Waveform
Generator
D
D
PORT
D
DDR
OCnx
Q
Q
Q
ATmega329P/3290P
1
0
Figure 17-4
shows a sim-
OCnx
Pin
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