ATMEGA3250-16AUR Atmel, ATMEGA3250-16AUR Datasheet - Page 138

• Manufacturer Part Number: ATMEGA3250-16AUR
• Description: MCU AVR 32K FLASH 16MHZ 100TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA3250-16AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 69
• 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: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

17.7.4
2570M–AVR–04/11
Phase Correct PWM Mode
The phase correct PWM mode (WGM21:0 = 1) provides a high resolution phase correct PWM
waveform generation option. The phase correct PWM mode is based on a dual-slope operation.
The counter counts repeatedly from BOTTOM to MAX and then from MAX to BOTTOM. In non-
inverting Compare Output mode, the Output Compare (OC2A) is cleared on the compare match
between TCNT2 and OCR2A while counting up, and set on the compare match while counting
down. In inverting Output Compare mode, the operation is inverted. The dual-slope operation
has lower maximum operation frequency than single slope operation. However, due to the sym-
metric feature of the dual-slope PWM modes, these modes are preferred for motor control
applications.
The PWM resolution for the phase correct PWM mode is fixed to eight bits. In phase correct
PWM mode the counter is incremented until the counter value matches MAX. When the counter
reaches MAX, it changes the count direction. The TCNT2 value will be equal to MAX for one
timer clock cycle. The timing diagram for the phase correct PWM mode is shown on
The TCNT2 value is in the timing diagram shown as a histogram for illustrating the dual-slope
operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal
line marks on the TCNT2 slopes represent compare matches between OCR2A and TCNT2.
Figure 17-7. Phase Correct PWM Mode, Timing Diagram
The Timer/Counter Overflow Flag (TOV2) is set each time the counter reaches BOTTOM. The
Interrupt Flag can be used to generate an interrupt each time the counter reaches the BOTTOM
value.
In phase correct PWM mode, the compare unit allows generation of PWM waveforms on the
OC2A pin. Setting the COM2A1:0 bits to two will produce a non-inverted PWM. An inverted
PWM output can be generated by setting the COM2A1:0 to three (See
The actual OC2A value will only be visible on the port pin if the data direction for the port pin is
set as output. The PWM waveform is generated by clearing (or setting) the OC2A Register at the
compare match between OCR2A and TCNT2 when the counter increments, and setting (or
clearing) the OC2A Register at compare match between OCR2A and TCNT2 when the counter
TCNTn
OCnx
OCnx
Period
1
2
ATmega325/3250/645/6450
3
Table 17-5 on page
OCnx Interrupt Flag Set
OCRnx Update
TOVn Interrupt Flag Set
(COMnx1:0 = 2)
(COMnx1:0 = 3)
Figure
17-7.
144).
138