Datasheet

115
7593L–AVR–09/12
AT90USB64/128
15. 16-bit Timer/Counter (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 (that is, 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)
15.1 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, that is, TCNT1 for accessing Timer/Counter1 counter value and so on.
A simplified block diagram of the 16-bit Timer/Counter is shown in Figure 15-1 on page 116. For
the actual placement of I/O pins, see “Pinout Atmel AT90USB64/128-TQFP.” 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 Timer/Counter (Timer/Counter1 and
Timer/Counter3)” on page 115.
The Power Reduction Timer/Counter1 bit, PRTIM1, in “PRR0 – Power Reduction Register 0” on
page 54 must be written to zero to enable Timer/Counter1 module.
The Power Reduction Timer/Counter3 bit, PRTIM3, in “PRR1 – Power Reduction Register 1” on
page 55 must be written to zero to enable Timer/Counter3 module.