ATMEGA165P_0611 Datasheet, PDF (84/368 Pages) ATMEL Corporation – 8-bit Microcontroller with 16K Bytes In-System Programmable Flash

13. 8-bit Timer/Counter0 with PWM
13.1 Features
13.2 Overview
• Single Compare Unit Counter
• Clear Timer on Compare Match (Auto Reload)
• Glitch-free, Phase Correct Pulse Width Modulator (PWM)
• Frequency Generator
• External Event Counter
• 10-bit Clock Prescaler
• Overflow and Compare Match Interrupt Sources (TOV0 and OCF0A)
Timer/Counter0 is a general purpose, single compare unit, 8-bit Timer/Counter module. A simpli-
fied block diagram of the 8-bit Timer/Counter is shown in Figure 13-1. For the actual placement
of I/O pins, refer to ”Pinout ATmega165P” 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 95.
Figure 13-1. 8-bit Timer/Counter Block Diagram
TCCRn
count
clear
direction
Control Logic
BOTTOM
TOP
Timer/Counter
TCNTn
= 0 = 0xFF
=
clk_Tn
Clock Select
Edge
Detector
( From Prescaler )
Waveform
Generation
TOVn
(Int.Req.)
Tn
OCn
(Int.Req.)
OCn
OCRn
13.2.1 Registers
The Timer/Counter (TCNT0) and Output Compare Register (OCR0A) are 8-bit registers. Inter-
rupt request (abbreviated to Int.Req. in the figure) signals are all visible in the Timer Interrupt
Flag Register (TIFR0). All interrupts are individually masked with the Timer Interrupt Mask Reg-
ister (TIMSK0). TIFR0 and TIMSK0 are not shown in the figure.
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on
the T0 pin. The Clock Select logic block controls which clock source and edge the Timer/Counter
uses to increment (or decrement) its value. The Timer/Counter is inactive when no clock source
is selected. The output from the Clock Select logic is referred to as the timer clock (clk_T0).
84 ATmega165P
8019H–AVR–11/06