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8025I–AVR–02/09
ATmega48P/88P/168P/328P
13. 16-bit Timer/Counter1 with PWM
13.1 Features
• True 16-bit Design (i.e., Allows 16-bit PWM)
• Two independent Output Compare Units
• Double Buffered Output Compare Registers
• One Input Capture Unit
• Input Capture Noise Canceler
• Clear Timer on Compare Match (Auto Reload)
• Glitch-free, Phase Correct Pulse Width Modulator (PWM)
• Variable PWM Period
• Frequency Generator
• External Event Counter
• Four independent interrupt Sources (TOV1, OCF1A, OCF1B, and ICF1)
13.2 Overview
The 16-bit Timer/Counter unit allows accurate program execution timing (event management),
wave generation, and signal timing measurement.
Most register and bit references in this section are written in general form. A lower case “n”
replaces the Timer/Counter number, and a lower case “x” replaces the Output Compare unit
channel. However, when using the register or bit defines in a program, the precise form must be
used, i.e., TCNT1 for accessing Timer/Counter1 counter value and so on.
A simplified block diagram of the 16-bit Timer/Counter is shown in Figure 13-1. For the actual
placement of I/O pins, refer to ”Pinout ATmega48P/88P/168P/328P” 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 134.
The PRTIM1 bit in ”PRR – Power Reduction Register” on page 45 must be written to zero to
enable Timer/Counter1 module.
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