Datasheet
133
8011O–AVR–07/10
ATmega164P/324P/644P
Table 13-3 on page 133 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to
the fast PWM mode.
Note: 1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is set. In
this case the compare match is ignored, but the set or clear is done at BOTTOM. See Section
“13.9.3” on page 124. for more details.
Table 13-4 on page 133 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to
the phase correct or the phase and frequency correct, PWM mode.
Note: 1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is set. See
Section “13.9.4” on page 126. for more details.
• Bit 1:0 – WGMn1:0: Waveform Generation Mode
Combined with the WGMn3:2 bits found in the TCCRnB Register, these bits control the counting
sequence of the counter, the source for maximum (TOP) counter value, and what type of wave-
form generation to be used, see Table 13-5 on page 134. Modes of operation supported by the
Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare match (CTC) mode,
and three types of Pulse Width Modulation (PWM) modes. (See Section “13.9” on page 123.).
Table 13-3. Compare Output Mode, Fast PWM
(1)
COMnA1/COMnB1 COMnA0/COMnB0 Description
0 0 Normal port operation, OCnA/OCnB disconnected.
01
WGMn3:0 = 14 or 15: Toggle OC1A on Compare
Match, OC1B disconnected (normal port operation).
For all other WGM1 settings, normal port operation,
OC1A/OC1B disconnected.
10
Clear OCnA/OCnB on Compare Match, set
OCnA/OCnB at BOTTOM (non-inverting mode)
11
Set OCnA/OCnB on Compare Match, clear
OCnA/OCnB at BOTTOM (inverting mode)
Table 13-4. Compare Output Mode, Phase Correct and Phase and Frequency Correct
PWM
(1)
COMnA1/COMnB1 COMnA0/COMnB0 Description
0 0 Normal port operation, OCnA/OCnB disconnected.
01
WGMn3:0 = 9 or 11: Toggle OCnA on Compare
Match, OCnB disconnected (normal port operation).
For all other WGM1 settings, normal port operation,
OC1A/OC1B disconnected.
10
Clear OCnA/OCnB on Compare Match when up-
counting. Set OCnA/OCnB on Compare Match when
downcounting.
11
Set OCnA/OCnB on Compare Match when up-
counting. Clear OCnA/OCnB on Compare Match
when downcounting.