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7593L–AVR–09/12
AT90USB64/128
When the OCnA, OCnB or OCnC is connected to the pin, the function of the COMnx1:0 bits is
dependent of the WGMn3:0 bits setting.
Table 15-1 shows the COMnx1:0 bit functionality when
the WGMn3:0 bits are set to a normal or a CTC mode (non-PWM).
Table 15-2 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the fast
PWM 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
the phase correct and frequency correct PWM mode.
Table 15-1.
Compare Output mode, non-PWM.
COMnA1/COMnB1/
COMnC1
COMnA0/COMnB0/
COMnC0
Description
00
Normal port operation, OCnA/OCnB/OCnC
disconnected.
0
1
Toggle OCnA/OCnB/OCnC on compare match.
10
Clear OCnA/OCnB/OCnC on compare match (set
output to low level).
11
Set OCnA/OCnB/OCnC on compare match (set
output to high level).
Table 15-2.
Compare Output mode, fast PWM.
COMnA1/COMnB1/
COMnC0
COMnA0/COMnB0/
COMnC0
Description
00
Normal port operation, OCnA/OCnB/OCnC
disconnected.
01
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.
10
Clear OCnA/OCnB/OCnC on compare match, set
OCnA/OCnB/OCnC at TOP
11
Set OCnA/OCnB/OCnC on compare match, clear
OCnA/OCnB/OCnC at TOP