ATMEGA48_09 Datasheet, PDF (86/340 Pages) ATMEL Corporation – 8-bit Microcontroller with 8K Bytes In-System Programmable Flash

12. 8-bit Timer/Counter0 with PWM
Timer/Counter0 is a general purpose 8-bit Timer/Counter module, with two independent Output
Compare Units, and with PWM support. It allows accurate program execution timing (event man-
agement) and wave generation. The main features are:
• Two Independent Output Compare Units
• Double Buffered Output Compare Registers
• Clear Timer on Compare Match (Auto Reload)
• Glitch Free, Phase Correct Pulse Width Modulator (PWM)
• Variable PWM Period
• Frequency Generator
• Three Independent Interrupt Sources (TOV0, OCF0A, and OCF0B)
12.1 Overview
A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 12-1. For the actual
placement of I/O pins, refer to “Pinout ATmega48/88/168” on page 2. CPU accessible I/O Regis-
ters, 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 “8-bit Timer/Counter Register Description” on page 97.
The PRTIM0 bit in “Power Reduction Register - PRR” on page 39 must be written to zero to
enable Timer/Counter0 module.
Figure 12-1. 8-bit Timer/Counter Block Diagram
Count
Clear
Control Logic
Direction
clk_Tn
Timer/Counter
TCNTn
=
TOP BOTTOM
Prescaler
=
=0
OCnA
(Int.Req.)
Waveform
Generation
TOVn
(Int.Req.)
T/C
Oscillator
clk_I/O
TOSC1
TOSC2
OCnA
OCRnA
=
OCRnB
Fixed
TOP
Value
OCnB
(Int.Req.)
Waveform
Generation
OCnB
TCCRnA
TCCRnB
86 ATmega48/88/168 Automotive
7530H–AVR–02/09