Page 50 - DEC40053 Ebook_Timer

example:-

Assume XTAL=10MHz.

1. Find the clock period fed into Timer0 if the

prescaler option 256 is chosen.

2. Show the largest time delay that can be

obtained using this prescaler option.

Answer:-

1) 1/4 x 10MHz = 2.5MHz and

1/256 x 2.5MHz = 9762.625 Hz due to 1:256

prescaler and

T = 1/9765.625Hz = 1024us = 1.024ms

2) To obtain the largest delay, make TMR0H

and TMR0L both 0. It will count from 0000

till FFFFh, roll over to raise the TMR0IF flag.

Time delay = (65535 - 0) + 1 x 1024us

Time delay = 67.109s

-41-