ATmega8U2/16U2/32U2
Table 16-3. Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
COMnA1/COMnB/
COMnC1
COMnA0/COMnB0/
COMnC0
Description
Normal port operation, OCnA/OCnB/OCnC
disconnected.
0
0
WGM1[3:0] = 8, 9 10 or 11: Toggle OC1A on
Compare Match, OC1B and OC1C disconnected
(normal port operation). For all other WGM1
settings, normal port operation,
0
1
OC1A/OC1B/OC1C disconnected.
Clear OCnA/OCnB/OCnC on compare match
when up-counting. Set OCnA/OCnB/OCnC on
compare match when downcounting.
1
1
0
1
Set OCnA/OCnB/OCnC on compare match when
up-counting. Clear OCnA/OCnB/OCnC on
compare match when downcounting.
Note:
A special case occurs when OCRnA/OCRnB/OCRnC equals TOP and
COMnA1/COMnB1//COMnC1 is set. See “Phase Correct PWM Mode” on page 99. for more
details.
• Bit 1:0 – WGMn1:0: Waveform Generation Mode
Combined with the WGMn[3:2] bits found in the TCCRnB Register, these bits control the count-
ing sequence of the counter, the source for maximum (TOP) counter value, and what type of
waveform generation to be used, see Table 16-4. 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 “Modes of Operation” on page
96.).
131
7799D–AVR–11/10
ATMEL [ ATMEL ]
