ATMEGA644A-PU Atmel, ATMEGA644A-PU Datasheet - Page 149
![IC MCU AVR 64K FLASH 40PDIP](/photos/6/70/67049/453-40-dip_sml.jpg)
ATMEGA644A-PU
Manufacturer Part Number
ATMEGA644A-PU
Description
IC MCU AVR 64K FLASH 40PDIP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644A-PU
Core Processor
AVR
Core Size
8-Bit
Speed
20MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
32
Program Memory Size
64KB (32K x 16)
Program Memory Type
FLASH
Eeprom Size
2K x 8
Ram Size
4K x 8
Voltage - Supply (vcc/vdd)
1.8 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
40-DIP (0.600", 15.24mm)
Processor Series
ATmega
Core
AVR
Data Bus Width
8 bit
Data Ram Size
4 KB
Interface Type
JTAG, TWI, SPI, USART
Maximum Clock Frequency
20 MHz
Number Of Programmable I/os
32
Number Of Timers
3
Operating Supply Voltage
3.3 V
Maximum Operating Temperature
+ 85 C
Mounting Style
Through Hole
Minimum Operating Temperature
- 40 C
Operating Temperature Range
- 40 C to + 85 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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16.8
8272A–AVR–01/10
Timer/Counter Timing Diagrams
In phase correct PWM mode, the compare unit allows generation of PWM waveforms on the
OC2x pin. Setting the COM2x1:0 bits to two will produce a non-inverted PWM. An inverted PWM
output can be generated by setting the COM2x1:0 to three. TOP is defined as 0xFF when
WGM2:0 = 3, and OCR2A when MGM2:0 = 7 (See
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 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 follow-
ing 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.
164A/164PA/324A/324PA/644A/644PA/1284/1284P
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 16-8 on page 150
contains timing data for basic Timer/Counter operation. The figure
Figure 16-7 on page 148
f
OCnxPCPWM
Figure 16-7 on page
=
Table 16-4 on page
----------------- -
N 510
f
clk_I/O
⋅
OCnx has a transition from high to low
148. When the OCR2A value
I/O
155). The actual OC2x
should be replaced by
149
T2
)
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