Datasheet

Section 14 Timer Z
Rev. 3.00 Mar. 15, 2006 Page 240 of 526
REJ09B0060-0300
B. External clock operation
An external clock input pin (TCLK) can be selected by bits TPSC2 to TPSC0 in TCR, and
a detection edge can be selected by bits CKEG1 and CKEG0. To detect an external clock,
the rising edge, falling edge, or both edges can be selected. The pulse width of the external
clock needs two or more system clocks. Note that an external clock does not operate
correctly with the lower pulse width.
Figure 14.11 illustrates the detection timing of the rising and falling edges.
TCNT
External clock
input pin
TCNT input
N-1 N N+1
φ
Figure 14.11 Count Timing at External Clock Operation (Both Edges Detected)