HD64F3437TF16 Datasheet, PDF (229/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

External Clock: If external clock input (TMCI) is selected, the timer counter can increment on
the rising edge, the falling edge, or both edges of the external clock signal. Figure 9.3 shows
incrementation on both edges of the external clock signal.
The external clock pulse width must be at least 1.5 system clock (ø) periods for incrementation on
a single edge, and at least 2.5 system clock periods for incrementation on both edges. The counter
will not increment correctly if the pulse width is shorter than these values.
ø
External clock
source (TMCI)
TCNT clock
pulse
TCNT
N–1
N
Figure 9.3 Count Timing for External Clock Input
N+1
200