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OVIEH/OVIEL in TCSRF and IENTFH/IENTFL in IENR2 are both 1, an interrupt
request is sent to the CPU.
2. TCF increment timing
TCF is incremented by clock input (internal clock or external event input).
a. Internal clock operation
Bits CKSH2 to CKSH0 or CKSL2 to CKSL0 in TCRF select one of four internal clock
sources (ø/32, ø/16, ø/4, or øw/4) created by dividing the system clock (ø or øw).
b. External event operation
External event input is selected by clearing CKSL2 to 0 in TCRF. TCF can increment on
either the rising or falling edge of external event input. External event edge selection is set
by IEG3 in the interrupt controller’s IEGR register. An external event pulse width of at
least 2 system clocks (ø) is necessary. Shorter pulses will not be counted correctly.