Datasheet

111
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
14. 16-bit Timers/Counters (Timer/Counter1 and Timer/Counter3)
The 16-bit Timer/Counter unit allows accurate program execution timing (event management), wave generation,
and signal timing measurement. The main features are:
•
True 16-bit Design (i.e., Allows 16-bit PWM)
• Three 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
• Ten independent interrupt sources (TOV1, OCF1A, OCF1B, OCF1C, ICF1, TOV3, OCF3A, OCF3B, OCF3C, and
ICF3)
14.1 Overview
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 14-1 on page 112. For the actual
placement of I/O pins, see “Pinout” on page 3. 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 “16-bit Timers/Counters
(Timer/Counter1 and Timer/Counter3)” on page 111.
The Power Reduction Timer/Counter1 bit, PRTIM1, in “Power Reduction Register 0 - PRR0” on page 47 must
be written to zero to enable Timer/Counter1 module.
The Power Reduction Timer/Counter3 bit, PRTIM3, in “Power Reduction Register 1 - PRR1” on page 48 must
be written to zero to enable Timer/Counter3 module.