Revision as of 15:02, 18 November 2014

Basics

Timers come in handy when you want to set some time interval like your alarm. This can be very precise to a few microseconds. Timers/Counters are essential part of any modern MCU. Remember it is the same hardware unit inside the MCU that is used either as Timers or Counter. Timers/counters are an independent unit inside a micro-controller. They basically run independently of what task CPU is performing. Hence they come in very handy, and are primarily used for the following:

Internal Timer: As an internal timer the unit, ticks on the oscillator frequency. The oscillator frequency can be directly feed to the timer or it can be pre-scaled. In this mode it used generate precise delays. Or as precise time counting machine.
External Counter: In this mode the unit is used to count events on a specific external pin on a MCU.
Pulse width Modulation(PWM) Generator: PWM is used in speed control of motors and various other applications.

Timers/Counters in AVR

Timer 0

Timer 0 Registers

TCNT0: Timer/Counter Register 0

Timer/Counter 0
TCNT0
D7	D6	D5	D4	D3	D2	D1	D0

TCCR0: Timer/Counter Control Register

TCCR0
D7	D6	D5	D4	D3	D2	D1	D0
FOC0	WGM00	COM01	COM00	WGM01	CS02	CS01	CS00

D6	D3	PWM
WGM00	WGM01	Mode
0	0	Normal
0	1	CTC (Clear timer on compare match)
1	0	PWM (Phase correct)
1	1	Fast PWM

Timer 1

Timer 2

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 |D7||D6||D5||D4||D3||D2||D1||D0
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-====TCCR0: Timer/Counter Control Register====
-{| class="wikitable floatright" style="float:right; background-color:#3DA8BB;"
-!colspan = '8'|TCCR0
-|-
-|D7||D6||D5||D4||D3||D2||D1||D0
-|-
-|FOC0||WGM00||COM01||COM00||WGM01||CS02||CS01||CS00
-|}
 ====TCCR0: Timer/Counter Control Register====
 {| class="wikitable floatright" style="float:right; background-color:#3DA8BB;"

Difference between revisions of "AVR Timer programming"