ATMEGA645A-AU Atmel, ATMEGA645A-AU Datasheet - Page 103

• Manufacturer Part Number: ATMEGA645A-AU
• Description: IC MCU AVR 64K FLASH 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA645A-AU

• 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: 54
• 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: 64-TQFP
• Processor Series: ATmega
• Core: AVR
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: SPI, USART
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 54
• Number Of Timers: 3
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

14.8
8285B–AVR–03/11
Timer/Counter Timing Diagrams
ATmega165A/165PA/325A/325PA/3250A/3250PA/6
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
there is no Compare Match. The point of this transition is to guarantee symmetry around BOT-
TOM. There are two cases that give a transition without Compare Match.
• OCR0A changes its value from MAX, like in
• The timer starts counting from a value higher than the one in OCR0A, and for that reason
The Timer/Counter is a synchronous design and the timer clock (clk
clock enable signal in the following figures. 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 14-8. Timer/Counter Timing Diagram, no Prescaling
Figure 14-9
Figure 14-9. Timer/Counter Timing Diagram, with Prescaler (f
Figure 14-10
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.
TCNTn
TCNTn
(clk
(clk
TOVn
TOVn
clk
clk
clk
clk
I/O
I/O
I/O
I/O
Tn
Tn
/1)
/8)
shows the same timing data, but with the prescaler enabled.
shows the setting of OCF0A in all modes except CTC mode.
Figure 14-8
MAX - 1
MAX - 1
contains timing data for basic Timer/Counter operation. The figure
Figure 14-7
OCn has a transition from high to low even though
MAX
MAX
Figure
14-7. When the OCR0A value is MAX the
BOTTOM
BOTTOM
clk_I/O
/8)
T0
) is therefore shown as a
BOTTOM + 1
BOTTOM + 1
103