ATMEGA325-16AJ ATMEL [ATMEL Corporation], ATMEGA325-16AJ Datasheet - Page 89

• Manufacturer Part Number: ATMEGA325-16AJ
• Description: 8-bit Microcontroller with In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Timer/Counter Timing
Diagrams
2570A–AVR–09/04
•
The Timer/Counter is a synchronous design and the timer clock (clk
shown as a clock enable signal in the following figures. The figures include information
on when Interrupt Flags are set. Figure 34 contains timing data for basic Timer/Counter
operation. The figure shows the count sequence close to the MAX value in all modes
other than phase correct PWM mode.
Figure 34. Timer/Counter Timing Diagram, no Prescaling
Figure 35 shows the same timing data, but with the prescaler enabled.
Figure 35. Timer/Counter Timing Diagram, with Prescaler (f
Figure 36 shows the setting of OCF0A in all modes except CTC mode.
Figure 36. Timer/Counter Timing Diagram, Setting of OCF0A, with Prescaler (f
TCNTn
TCNTn
TCNTn
(clk
(clk
(clk
OCRnx
OCFnx
TOVn
TOVn
clk
clk
clk
clk
clk
clk
I/O
I/O
I/O
The timer starts counting from a value higher than the one in OCR0A, and for that
reason misses the Compare Match and hence the OCn change that would have
happened on the way up.
I/O
I/O
I/O
Tn
Tn
Tn
/1)
/8)
/8)
OCRnx - 1
MAX - 1
MAX - 1
ATmega325/3250/645/6450
OCRnx
MAX
MAX
OCRnx Value
OCRnx + 1
BOTTOM
BOTTOM
clk_I/O
/8)
T0
) is therefore
BOTTOM + 1
BOTTOM + 1
OCRnx + 2
clk_I/O
/8)
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