Datasheet

65
ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
11. 8-bit Timer/Counter0 with PWM
11.1 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)
11.2 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 11-1. For the actual placement of I/O pins,
refer to “Pinout ATtiny25/45/85” 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 77.
Figure 11-1. 8-bit Timer/Counter Block Diagram
11.2.1 Registers
The Timer/Counter (TCNT0) and Output Compare Registers (OCR0A and OCR0B) are 8-bit registers. Interrupt
request (abbreviated to Int.Req. in the figure) signals are all visible in the Timer Interrupt Flag Register (TIFR). All
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