ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 122
![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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14.8.1
14.9
14.9.1
14.9.2
122
Modes of Operation
ATmega164P/324P/644P
Compare Output Mode and Waveform Generation
Normal Mode
Clear Timer on Compare Match (CTC) Mode
The Waveform Generator uses the COMnx1:0 bits differently in normal, CTC, and PWM modes.
For all modes, setting the COMnx1:0 = 0 tells the Waveform Generator that no action on the
OCnx Register is to be performed on the next compare match. For compare output actions in the
non-PWM modes refer to
page
page
A change of the COMnx1:0 bits state will have effect at the first compare match after the bits are
written. For non-PWM modes, the action can be forced to have immediate effect by using the
FOCnx strobe bits.
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare pins, is
defined by the combination of the Waveform Generation mode (WGMn3:0) and Compare Output
mode (COMnx1:0) bits. The Compare Output mode bits do not affect the counting sequence,
while the Waveform Generation mode bits do. The COMnx1:0 bits control whether the PWM out-
put generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes
the COMnx1:0 bits control whether the output should be set, cleared or toggle at a compare
match
For detailed timing information refer to
The simplest mode of operation is the Normal mode (WGMn3:0 = 0). In this mode the counting
direction is always up (incrementing), and no counter clear is performed. The counter simply
overruns when it passes its maximum 16-bit value (MAX = 0xFFFF) and then restarts from the
BOTTOM (0x0000). In normal operation the Timer/Counter Overflow Flag (TOVn) will be set in
the same timer clock cycle as the TCNTn becomes zero. The TOVn Flag in this case behaves
like a 17th bit, except that it is only set, not cleared. However, combined with the timer overflow
interrupt that automatically clears the TOVn Flag, the timer resolution can be increased by soft-
ware. There are no special cases to consider in the Normal mode, a new counter value can be
written anytime.
The Input Capture unit is easy to use in Normal mode. However, observe that the maximum
interval between the external events must not exceed the resolution of the counter. If the interval
between events are too long, the timer overflow interrupt or the prescaler must be used to
extend the resolution for the capture unit.
The Output Compare units can be used to generate interrupts at some given time. Using the
Output Compare to generate waveforms in Normal mode is not recommended, since this will
occupy too much of the CPU time.
In Clear Timer on Compare or CTC mode (WGMn3:0 = 4 or 12), the OCRnA or ICRn Register
are used to manipulate the counter resolution. In CTC mode the counter is cleared to zero when
the counter value (TCNTn) matches either the OCRnA (WGMn3:0 = 4) or the ICRn (WGMn3:0 =
12). The OCRnA or ICRn define the top value for the counter, hence also its resolution. This
mode allows greater control of the compare match output frequency. It also simplifies the opera-
tion of counting external events.
132, and for phase correct and phase and frequency correct PWM refer to
133.
(See “Compare Match Output Unit” on page
Table 14-2 on page
“Timer/Counter Timing Diagrams” on page
132. For fast PWM mode refer to
121.)
Table 14-3 on
Table 14-4 on
129.
7674F–AVR–09/09
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