ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 149

• 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

15.8
7674F–AVR–09/09
Timer/Counter Timing Diagrams
The PWM waveform is generated by clearing (or setting) the OC2x Register at the compare
match between OCR2x and TCNT2 when the counter increments, and setting (or clearing) the
OC2x Register at compare match between OCR2x and TCNT2 when the counter decrements.
The PWM frequency for the output when using phase correct PWM can be calculated by the fol-
lowing equation:
The N variable represents the prescale factor (1, 8, 32, 64, 128, 256, or 1024).
The extreme values for the OCR2A Register represent special cases when generating a PWM
waveform output in the phase correct PWM mode. If the OCR2A is set equal to BOTTOM, the
output will be continuously low and if set equal to MAX the output will be continuously high for
non-inverted PWM mode. For inverted PWM the output will have the opposite logic values.
At the very start of period 2 in
even though there is no Compare Match. The point of this transition is to guarantee symmetry
around BOTTOM. There are two cases that give a transition without Compare Match.
• OCR2A changes its value from MAX, like in
• The timer starts counting from a value higher than the one in OCR2A, and for that reason
The following figures show the Timer/Counter in synchronous mode, and the timer clock (clk
is therefore shown as a clock enable signal. In asynchronous mode, clk
the Timer/Counter Oscillator clock. The figures include information on when Interrupt Flags are
set.
shows the count sequence close to the MAX value in all modes other than phase correct PWM
mode.
Figure 15-8. Timer/Counter Timing Diagram, no Prescaling
is MAX the OCn pin value is the same as the result of a down-counting compare match. To
ensure symmetry around BOTTOM the OCn value at MAX must correspond to the result of an
up-counting Compare Match.
misses the Compare Match and hence the OCn change that would have happened on the way
up.
Figure 15-8 on page 149
TCNTn
(clk
TOVn
clk
clk
I/O
I/O
Tn
/1)
MAX - 1
contains timing data for basic Timer/Counter operation. The figure
Figure 15-7 on page 148
f
OCnxPCPWM
MAX
Figure 15-7 on page
ATmega164P/324P/644P
=
-------------------- -
N
f
clk_I/O
510
OCnx has a transition from high to low
BOTTOM
148. When the OCR2A value
I/O
should be replaced by
BOTTOM + 1
149
T2
)