Datasheet

Section 12 Timer W
Rev. 6.00 Mar. 24, 2006 Page 181 of 412
REJ09B0142-0600
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.
TCNT
TCNT input
clock
Internal
clock
φ
N N+1 N+2
Rising edge
Figure 12.14 Count Timing for Internal Clock Source
TCNT
TCNT input
clock
External
clock
φ
NN+1N+2
Rising edge Rising edge
Figure 12.15 Count Timing for External Clock Source