The timer-0 module is a simple 8-bit UP counter. The clock source can be either the internal clock (fosc /4) or an external clock. When the clock source is external, the Timer-0 module can be programmed to increment on either the rising or falling clock edge. Timer-0 module has a programmable pre-scaler option. This pre-scaler can be assigned either to Timer-0 or the Watch dog timer, but not to both.
The Timer-0 Counter sets a flag T0IF (Timer-0 Interrupt Flag) when it overflows and can cause an interrupt at that time if that interrupt source has been enabled, (T0IE = 1), i.e., timer-0 interrupt enable bit = 1.