8-bit AVR Microcontroller

Internal Clock Source - Prescaler

The Timer/Counter can be clocked directly by the system clock (by setting the TCCR0B.CS0[2:0]=0x1). This provides the fastest operation, with a maximum Timer/Counter clock frequency equal to system clock frequency (fCLK_I/O). Alternatively, one of four taps from the prescaler can be used as a clock source. The prescaled clock has a frequency of either fCLK_I/O/8, fCLK_I/O/64, fCLK_I/O/256, or fCLK_I/O/1024.
Figure 1. Prescaler for Timer/Counter0