There are some features that is only available in 16 bit timer(timer/counter1). In generating PWM, you can use the top value to change the frequency and compare value to change the duty cycle. Phase and Frequency Correct mode timing diagram in phase correct mode, a period is from a top to the next top while phase and frequency correct mode a period is from a bottom to another bottom. The difference of phase correct mode and phase and frequency correct mode is that the output of phase correct mode is asymmetrical, while phase and frequency correct mode is symmetrical in a period. because the countter valueoperation is using two slope(incrementing and decrementing), the frequency will be In phase correct and phase and frequency corect, the counter value is incrementing to top and the decrementing from top to bottom. in fast PWM the counter for generating pwm frequency is only incrementing(one slope). In CTC mode, the counter resets when the counter value matches the OCRx register. In normal mode, the counter value is always incrementing and resets to bottom when overflow occurs. There ara 4 operation mode: normal, clear on timer compare match(CTC), fast pwm, phase correct pwm and phase and frequency correct pwm.

External clock is inserted from pin Tx on AVR. External clock is usually used for counter application. The prescaler is used to set the time resolution on your timer/counter. you can use the AVR clock source, using prescaled clock or external clock source. The register for setting the clock and modes are the TCCRx.Ĭlock source can be configured by setting the CS bit. you must set your clock source and operating mode. The captured event is detected from a pin ICPx or analog comparator.Īfter knowing the basic value, you must know some important setting for using the timer/counter. Input capture is a counter value which increments within the clock if there are captured events. When the counter value reach the top,it is called overflow.Ĭompare value is used to make a flag inside a counter period.The register is(OCRx).

The top can be set into fixed value or another register, like OCRx or ICRx.

Top value give you the maximal value of the counter before it resets to bottom(zero). The register for counter value is TCNTx(x shows the number of used timer). If you have the operating timer clock source on 1MHz, the counter value will be increasing with the speed 1MHz. There are registers for each values.Ĭounter value is increasing according to the clock source. There are some basic important value while using timer/counter: counter value, top value, compare value and inputcapture value. It is usually used to make application which require periodical event, counter from user, measuring event time or making a PWM(pulse width modulation) for controlling some device. Timer/Counter is a feature on avr which can count based on the clock source.

Codevision avr pwm