•
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.
Timer/Counter Timing
Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkT0) is therefore
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
clkI/O
clkTn
(clkI/O/1)
TCNTn
TOVn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
Figure 35 shows the same timing data, but with the prescaler enabled.
Figure 35. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
TOVn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
Figure 36 shows the setting of OCF0 in all modes except CTC mode.
78
ATmega32(L)
2503J–AVR–10/06
ATMEL [ ATMEL ]
