Question

What is the difference in the operation of a normal and a CTC mode of a timer?

(a) in CTC mode PWM is used

(b) here serial timer is monitored

(c) in CTC mode, timer counts up until contents of TCNT register becomes equal to the contents of OCR

(d) none of the mentioned

This question was posed to me in quiz.

Enquiry is from Timer Programming in section AVR Microcontroller of Microcontroller

Answer 1

Right choice is (c) in CTC mode, timer counts up until contents of TCNT register becomes equal to the contents of OCR

The best I can explain: In CTC mode, timer counts up until the contents of TCNT register becomes equal to the contents of OCR; then the timer will be cleared and the OCF0 flag will be set when the next clock occurs. In Normal mode, timer counts until max i.e. 0xFFH. When it rolls over from 0xFFH to 0x00H, it sets TOV(Timer Overflow).