ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 146
![MCU AVR 64KB FLASH 16MHZ 44QFN](/photos/12/13/121316/313-44-qfn_sml.jpg)
ATMEGA644P-A15MZ
Manufacturer Part Number
ATMEGA644P-A15MZ
Description
MCU AVR 64KB FLASH 16MHZ 44QFN
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644P-A15MZ
Package / Case
44-VQFN Exposed Pad
Voltage - Supply (vcc/vdd)
2.7 V ~ 5.5 V
Operating Temperature
-40°C ~ 125°C
Speed
16MHz
Number Of I /o
32
Eeprom Size
2K x 8
Core Processor
AVR
Program Memory Type
FLASH
Ram Size
4K x 8
Program Memory Size
64KB (64K x 8)
Data Converters
A/D 8x10b
Oscillator Type
Internal
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Connectivity
I²C, SPI, UART/USART
Core Size
8-Bit
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
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Manufacturer:
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Quantity:
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Part Number:
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Manufacturer:
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15.7.3
146
ATmega164P/324P/644P
Fast PWM Mode
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 TOP to a value close to BOTTOM when the counter is run-
ning 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 current
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 (WGM22:0 = 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 WGM22:0 = 3, and OCR2A when MGM22:0 = 7. In
non-inverting Compare Output mode, the Output Compare (OC2x) is cleared on the compare
match between TCNT2 and OCR2x, 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
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
shown as a histogram for illustrating the single-slope operation. The diagram includes
non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT2 slopes
represent compare matches between OCR2x and TCNT2.
clk_I/O
/2 when OCR2A is set to zero (0x00). The waveform frequency is defined by the following
Figure 15-6 on page
f
OCnx
=
------------------------------------------------------ -
2
TOV2
N
147. The TCNT2 value is in the timing diagram
Flag is set in the same timer clock cycle that the
f
clk_I/O
1
+
OCRnx
7674F–AVR–09/09
OC2A
=
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