Datasheet

132
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
The table 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/OCRnC equals TOP and COMnA1/COMnB1/COMnC1 is set. In
this case the compare match is ignored, but the set or clear is done at TOP. See “Fast PWM Mode” on
page 100. for more details.
The table shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the phase correct and
frequency correct PWM mode.
Note: 1. A special case occurs when OCRnA/OCRnB/OCRnC equals TOP and COMnA1/COMnB1//COMnC1 is set.
See “Phase Correct PWM Mode” on page 101. 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 waveform generation to be used,
see the table below. 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 (“Modes of
Operation” on page 98).
Table 14-2. Compare Output Mode, Fast PWM
(1)
COMnA1/COMnB1/COMnC0 COMnA0/COMnB0/COMnC0 Description
0 0
Normal port operation, OCnA/OCnB/OCnC
disconnected
0 1
WGM13:0 = 14 or 15: Toggle OC1A on Compare
Match, OC1B and OC1C disconnected (normal port
operation). For all other WGM1 settings, normal port
operation, OC1A/OC1B/OC1C disconnected.
1 0
Clear OCnA/OCnB/OCnC on compare match, set
OCnA/OCnB/OCnC at TOP
1 1
Set OCnA/OCnB/OCnC on compare match, clear
OCnA/OCnB/OCnC at TOP
Table 14-3. Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
(1)
COMnA1/COMnB/COMnC1 COMnA0/COMnB0/COMnC0 Description
0 0
Normal port operation, OCnA/OCnB/OCnC
disconnected.
0 1
WGM13:0 = 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, OC1A/OC1B/OC1C disconnected.
1 0
Clear OCnA/OCnB/OCnC on compare match when up-
counting. Set OCnA/OCnB/OCnC on compare match
when down-counting.
1 1
Set OCnA/OCnB/OCnC on compare match when up-
counting. Clear OCnA/OCnB/OCnC on compare match
when down-counting.