ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 119

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

8-bit Timer/Counter0
with PWM
Overview
Registers
2549K–AVR–01/07
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. The main features are:
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A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 37. For the
actual placement of I/O pins, refer to “TQFP-pinout ATmega640/1280/2560” 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 130.
Figure 37. 8-bit Timer/Counter Block Diagram
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 vis-
ible in the Timer Interrupt Flag Register (TIFR0). All interrupts are individually masked
with the Timer Interrupt Mask Register (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
The double buffered Output Compare Registers (OCR0A and OCR0B) are compared
with the Timer/Counter value at all times. The result of the compare can be used by the
Waveform Generator to generate a PWM or variable frequency output on the Output
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)
Timer/Counter
TCCRnA
OCRnA
TCNTn
OCRnB
ATmega640/1280/1281/2560/2561
=
=
Direction
Count
T0
Clear
).
Control Logic
TOP
=
TCCRnB
Value
BOTTOM
Fixed
TOP
clk
=
Tn
0
OCnA
(Int.Req.)
OCnB
(Int.Req.)
TOVn
(Int.Req.)
Clock Select
Generation
Generation
( From Prescaler )
Waveform
Waveform
Detector
Edge
OCnA
OCnB
Tn
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