.
Table 17-3. Compare Output Mode, non-PWM
COMnA1
COMnB1
COMnC1
COMnA0
COMnB0
COMnC0
Description
0
0
1
1
0
1
0
1
Normal port operation, OCnA/OCnB/OCnC disconnected.
Toggle OCnA/OCnB/OCnC on compare match.
Clear OCnA/OCnB/OCnC on compare match (set output to low level).
Set OCnA/OCnB/OCnC on compare match (set output to high level).
Table 17-4 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the fast
PWM mode.
Table 17-4. Compare Output Mode, Fast PWM
COMnA1
COMnB1
COMnC1
COMnA0
COMnB0
COMnC0
Description
0
0
Normal port operation, OCnA/OCnB/OCnC disconnected.
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.
0
1
Clear OCnA/OCnB/OCnC on compare match, set OCnA/OCnB/OCnC at
BOTTOM (non-inverting mode).
1
1
0
1
Set OCnA/OCnB/OCnC on compare match, clear OCnA/OCnB/OCnC at
BOTTOM (inverting mode).
Note:
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 BOTTOM. See “Fast PWM Mode” on page 150. for more details.
Table 17-5 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the phase
correct and frequency correct PWM mode.
Table 17-5. Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
COMnA1
COMnB1
COMnC1
COMnA0
COMnB0
COMnC0
Description
0
0
Normal port operation, OCnA/OCnB/OCnC disconnected.
WGM13:0 =9 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.
0
1
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 152. for more
details.
160
ATmega640/1280/1281/2560/2561
2549L–AVR–08/07
ATMEL [ ATMEL ]
