Datasheet

Section 13 Timer W
Rev. 3.00 Mar. 15, 2006 Page 204 of 526
REJ09B0060-0300
13.5 Operation Timing
13.5.1 TCNT Count Timing
Figure 13.14 shows the TCNT count timing when the internal clock source is selected. Figure
13.15 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 13.14 Count Timing for Internal Clock Source
TCNT
TCNT input
clock
External
clock
φ
N N+1
N+2
Rising edge Rising edge
Figure 13.15 Count Timing for External Clock Source