Revision as of 11:08, 24 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

D2	D1	D0	Clock Source
CS02	CS01	CS00	Freq
0	0	0	No Clock (Stopped)
0	0	1	Clk
0	1	0	Clk/8
0	1	1	Clk/64
1	0	0	Clk/256
1	0	1	Clk/1024
1	1	0	Clk/T0-Falling edge
1	1	1	Clk/T0-Rising Edge

|}

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

@@ Line 27: / Line 27: @@
 |}
+{| class="wikitable floatright" style="float:right; background-color:#3DA8BB;"
+!D2||D1||D0||Clock Source
+|-
+!CS02||CS01||CS00||Freq
+|-
+|0||0||0|| No Clock (Stopped)
+|-
+|0||0||1||Clk
+|-
+|0||1||0||Clk/8
+|-
+|0||1||1||Clk/64
+|-
+|1||0||0||Clk/256
+|-
+|1||0||1||Clk/1024
+|-
+|1||1||0||Clk/T0-Falling edge
+|-
+|1||1||1||Clk/T0-Rising Edge
+|}
+|}
 {| class="wikitable floatright" style="float:right; background-color:#3DA8BB;"
 !D6||D3||PWM

Difference between revisions of "AVR Timer programming"