Datasheet

Bit 0 – OCF1C: Timer/Counter1, Output Compare C Match Flag
This flag is set in the timer clock cycle after the counter (TCNT1) value matches the Output Compare
Register C (OCR1C).
Note that a forced output compare (FOC1C) strobe will not set the OCF1C flag.
OCF1C is automatically cleared when the Output Compare Match 1 C interrupt vector is executed.
Alternatively, OCF1C can be cleared by writing a logic one to its bit location.
Atmel ATmega64A [DATASHEET]
Atmel-8160E-ATmega64A_Datasheet_Complete-09/2015
191