1. ELE22MIC Lecture 18 The AVR Sleep Modes The ATMEGA128’s Timer System
Clock Sources
The 8-bit Timer 0 Modes
Clear Timer on Compare match (CTC)
Two Pulse Width Modulation (PWM) modes
Fast Pulse Width Modulation
Phase Correct Pulse Width Modulation

2. 8-bit Timer/Counter 0
The ATMEGA128 contains 4 timer modules. The Bilby is the device we use in lab sessions: an ATMEGA128 on a PCB.
Each module has a selection of possible clock or oscillator sources:
I/O Clock, System Clock
The Bilby’s main crystal is MHz,
An External low-power crystal connected to TOSC1 & TOSC2 pins.

3. 8-bit Timer/Counter 0 The Bilby’s main crystal is 7.3728MHz,
ATMEGA128 Current consumption with the main oscillator running is in the order of 5mA.
The Bilby’s low-power crystal connected to TOSC1 & TOSC2 pins.
The Bilby’s low power crystal is 32768Hz
The ATMEGA128 has sleep modes where only this counter remains active.
Total current consumption with a 32768Hz crystal clock running, in power-down sleep mode, is around 200nA (all other subsystems switched off).

4. Modes of Sleep - Sleep Depth

5. Modes of Sleep - Clock Domains

6. Power-Save Considerations
Every enabled CPU feature consumes extra current.
For example the Bandgap voltage reference consumes 10uA current.
The ultra-low power-down sleep mode power consumption can only be achieved IF the features can be switched off.. We can then achieve ultra-low power operation - suitable for miniature battery operation.

7. Timer / Counter 0 Main Features:
Timer/Counter0 is a general purpose, single channel, 8-bit Timer/Counter module. The main features are:
Single Channel Counter
Clear Timer on Compare Match (Auto Reload)

8. Timer / Counter 0
Glitch-free, Phase Correct Pulse Width Modulator (PWM)
Frequency Generator
10-bit Clock Prescaler
Overflow and Compare Match Interrupt Sources (TOV0 and OCF0)
Allows Clocking from External 32 kHz Watch Crystal Independent of the I/O Clock

9. 8-Bit Timer Block Diagram

10. 8-Bit Timer Block Diagram

11. 8-Bit Timer Counter Unit Block Diagram

12. 8-Bit Timer Output Compare Unit

13. CTC Mode Timing Diagram

14. Fast PWM Mode, Timing Diagram

15. Phase Correct PWM Mode, Timing Diagram

16. ULN2003

17. Stepper Motor

18. ULN2003