12.5
Operation Timing
12.5.1
TCNT Count Timing
Figure 12.14 shows the TCNT count timing when the internal clock source is selected. Figure
12.15 shows the timing when the external clock source is selected. The pulse width of the external
clock signal must be at least two system clock (φ) cycles; shorter pulses will not be counted
correctly.
Internal
clock
TCNT input
clock
TCNT
External
clock
TCNT input
clock
TCNT
Rev. 1.00, 11/03, page 172 of 376
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Rising edge
N
Figure 12.14 Count Timing for Internal Clock Source
Rising edge
N
Figure 12.15 Count Timing for External Clock Source
N+1
Rising edge
N+1
N+2
N+2