Rainbow Electronics ATmega128RFA1 - Manual (Page 226)

226
8266A-MCU Wireless-12/09
ATmega128RFA1
17 8-bit Timer/Counter0 with PWM
17.1 Features
• 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)
17.2 Overview
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 management) and wave generation.
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 section
"Pin Configurations" 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
"Register Description" on page
238 .
Figure 17-1. 8-bit Timer/Counter Block Diagram
Clock Select
Timer/Counter
DA
T
A B
US
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