Asynchronous Operation - Atmel ATmega8535L User Manual

8-bit Timer/Counter2
with PWM and
Asynchronous
Operation
Overview
2502K–AVR–10/06
Timer/Counter2 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)
•
Glitch-free, Phase Correct Pulse Width Modulator (PWM)
•
Frequency Generator
•
10-bit Clock Prescaler
•
Overflow and Compare Match Interrupt Sources (TOV2 and OCF2)
•
Allows Clocking from External 32 kHz Watch Crystal Independent of the I/O Clock
A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 53. For the
actual placement of I/O pins, refer to "Pinout ATmega8535" 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 "8-bit Timer/Counter Register Description" on
page 128.
Figure 53. 8-bit Timer/Counter Block Diagram
count
clear
direction
BOTTOM
Timer/Counter
TCNTn
=
OCRn
Synchronized Status Flags
Status Flags
ASSRn
TCCRn
Control Logic
clk
Tn
TOP
= 0 =
0xFF
OCn
(Int.Req.)
Synchronization Unit
Asynchronous Mode
Select (ASn)
ATmega8535(L)
T/C
Oscillator
Prescaler
Waveform
Generation
TOVn
(Int.Req.)
TOSC1
TOSC2
clk
I/O
OCn
clk
I/O
clk
ASY
117