ATmega48PA/88PA/168PA/328P
17. 8-bit Timer/Counter2 with PWM and Asynchronous Operation
17.1 Features
• Single Channel Counter
• Clear Timer on Compare Match (Auto Reload)
• Glitch-free, Phase Correct Pulse Width Modulator (PWM)
• Frequency Generator
• 10-bit Clock Prescaler
• Overflow and Compare Match Interrupt Sources (TOV2, OCF2A and OCF2B)
• Allows Clocking from External 32 kHz Watch Crystal Independent of the I/O Clock
17.2 Overview
Timer/Counter2 is a general purpose, single channel, 8-bit Timer/Counter module. A simplified
block diagram of the 8-bit Timer/Counter is shown in Figure 17-1. For the actual placement of
I/O pins, refer to ”Pinout ATmega48PA/88PA/168PA/328P” on page 2. CPU accessible I/O Reg-
isters, including I/O bits and I/O pins, are shown in bold. The device-specific I/O Register and bit
locations are listed in the ”Register Description” on page 158.
The PRTIM2 bit in ”Minimizing Power Consumption” on page 42 must be written to zero to
enable Timer/Counter2 module.
Figure 17-1. 8-bit Timer/Counter Block Diagram
Count
TOVn
(Int.Req.)
Clear
Direction
Control Logic
Clock Select
clkTn
Edge
Detector
Tn
TOP
BOTTOM
( From Prescaler )
Timer/Counter
TCNTn
=
= 0
OCnA
(Int.Req.)
Waveform
Generation
OCnA
=
OCRnA
Fixed
TOP
Value
OCnB
(Int.Req.)
Waveform
Generation
OCnB
=
OCRnB
TCCRnA
TCCRnB
144
8161D–AVR–10/09
ATMEL [ ATMEL ]
