Hitachi H8/3664 Hardware Manual page 195

TCNTV Increment Timing: TCNTV is incremented by an input (internal or external) clock.
• Internal clock
One of six clocks (ø/128, ø/64, ø/32, ø/16, ø/8, ø/4) divided from the system clock (ø) can be
selected by bits CKS2 to CKS0 in TCRV0 and bit ICKS0 in TCRV1. Figure 11.2 shows the
timing.
ø
Internal clock
TCNTV input
clock
TCNTV
• External clock
Incrementation on the rising edge, falling edge, or both edges of the external clock can be
selected by bits CKS2 to CKS0 in TCRV0.
The external clock pulse width should be at least 1.5 system clocks (ø) when a single edge is
counted, and at least 2.5 system clocks when both edges are counted. Shorter pulses will not be
counted correctly.
Figure 11.3 shows the timing when both the rising and falling edges of the external clock are
selected.
ø
TMCIV
(External clock
input pin)
TCNTV input
clock
TCNTV
N – 1
Figure 11.2 Increment Timing with Internal Clock
N – 1
Figure 11.3 Increment Timing with External Clock
N
N
N + 1
N + 1
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