MICROPROCESSOR AND MICROCONTROLLER

Detailed explanation-1: -There are eight prescaler options for the Timer0 module ranging from 1:2 to 1:256. The prescale values are selectable via the PS<2:0> bits of the OPTION REG register.

Detailed explanation-2: -Timer 0 can be operated both as a timer and counter. All the parts to the left are the clock source circuits. T0CON (Timer 0 Control) register is used to program the timer and includes the bits shown in figure (T0CS, PSA etc.) The clock source can be internal or external and is controlled by T0CS bit.

Detailed explanation-3: -A prescaler divides down the clock signals used for the timer, giving reduced overflow rates. The rate can be set to a number of possible values. The exact values are chip-dependent; e.g., for the PIC16F877A values area a number of values are available ranging from 1:1 to 1:256.

Detailed explanation-4: -Prescalar is a configurable clock-divider circuit. It can be used to divide the clock frequency input to the timer module. For example, if the instruction clock is 5MHz and we use a prescaler of 2 to divide it which effectively make the clock 2.5MHz. So each counting time will increase from 0.2 µs to 0.4 µs.

Detailed explanation-5: -Timer 0 is TL0 and Timer 1 is TH0. Both the timers count from 0 to 255 and in case of overflow, reset back to 0. All the bits that are of Timer 1 will now be tied to TH0.