8.3.1 Default Clock Source
The device is shipped with internal RC oscillator at 8.0 MHz and with the fuse CKDIV8 programmed,
resulting in 1.0 MHz system clock. The startup time is set to maximum and time-out
period enabled. (CKSEL = "0010", SUT = "10", CKDIV8 = "0"). The default setting ensures that
all users can make their desired clock source setting using any available programming interface.