Question

Assume that XTAL = 4MHz, We are generating a square wave with a period of 4msec on bit 0 of PORTC. Find the TMR0L, TMR0H value needed to generate this period. Using Timer0 in 16-bit mode, no prescaler mode

Answer 1

Answer :- The period of wave is 4 ms. Thus for 50% duty cycle, the high time and low time are 2 ms. So timer must be programmed to give interrupt after 2 ms.

The value of timer frequency is-

4000000 H= 4000000 Hz ftimer

The time period value is-

Ttimer 4000000

Delay value needed is 2 ms. Thus the count value for the timer is-

2x10-3 n = - 8000 1 4000000

Thus the 16-bit representation of 8000 is-

$8000=0001\_1111\_0100\_0000=0x1F40$

Since timer over flows when reaches 0xFFFF, hence the timer value will be-

OXFFFF-Ox-20 = 0XF0BF

Hence the timer values are-

TMROH 0XEO, TMROL = 0XBF