1. Timers in Hardware ECE152

2. Overview Why are timers important – Watchdog – Task switching – Accurate time of day Can use polling or interrupts

3. Possible Timers Timer0 (8 Bit) Timer1 (16 bit) Timer2 (8 Bit) - Real Time Clock Timer3 (16 Bit)

4. Timer0 Important Registers TCCR0A – Timer Counter Control A TCCR0B – Timer Counter Control B TCNT0- Timer Count OCR0A – Output Compare Register A

5. Timer0 Modes In general we use Clear Timer Counter (CTC) mode

6. Clock Source Based on CLK IO (1 MHz) In groups, calculate the maximum and minimum time the can be counted for each selection.

7. Example Simple Timer0 Lets walk through the configuration registers and make a simple program to blink some LEDs

8. Things to Remember To use a piece of hardware in a microcontroller: – Read the data sheet – Go though the registers one by one and decide on bit values When in doubt, set to default