Datasheet

136
7810C–AVR–10/12
Atmel ATmega328P [Preliminary]
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” on page 2. CPU accessible I/O Registers, 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 “Reg-
ister Description” on page 150.
The PRTIM2 bit in “Minimizing Power Consumption” on page 40 must be written to zero to
enable Timer/Counter2 module.
Figure 17-1. 8-bit Timer/Counter Block Diagram
Clock Select
Timer/Counter
DATA BUS
OCRnA
OCRnB
=
=
TCNTn
Waveform
Generation
Waveform
Generation
OCnA
OCnB
=
Fixed
TOP
Value
Control Logic
= 0
TOP BOTTOM
Count
Clear
Direction
TOVn
(Int.Req.)
OCnA
(Int.Req.)
OCnB
(Int.Req.)
TCCRnA TCCRnB
Tn
Edge
Detector
( From Prescaler )
clk
Tn