# input clock frequency (before any prescaling is performed) in Hz. This value may\r
# differ from F_CPU if prescaling is used on the latter, and is required as the\r
# raw input clock is fed directly to the PLL sections of the AVR for high speed\r
# input clock frequency (before any prescaling is performed) in Hz. This value may\r
# differ from F_CPU if prescaling is used on the latter, and is required as the\r
# raw input clock is fed directly to the PLL sections of the AVR for high speed\r