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8266A-MCU Wireless-12/09
ATmega128RFA1
Table 18-3. Compare Output Mode, Fast PWM
COMnA1
COMnB1
COMnC1
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 BOTTOM (non-inverting mode).
1 1
Set OCnA/OCnB/OCnC on compare match, clear
OCnA/OCnB/OCnC at BOTTOM (inverting 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 BOTTOM. See "Fast PWM Mode" on page 258 for more
details.
Table 18-4 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the
phase correct and phase and frequency correct PWM mode.
Table 18-4. Compare Output Mode, Phase Correct and Phase/Frequency Correct
PWM
COMnA1
COMnB1
COMnC1
COMnA0
COMnB0
COMnC0 Description
0 0 Normal port operation, OCnA/OCnB/OCnC disconnected.
0 1
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.
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.
Note: 1. A special case occurs when OCRnA/OCRnB/OCRnC equals TOP and
COMnA1/COMnB1/COMnC1 is set. See "Phase and Frequency Correct PWM
Mode" on page 262 for more details.
18.9 Modes of Operation
The mode of operation i.e., the behavior of the Timer/Counter and the Output Compare
pins, is defined by the combination of the Waveform Generation mode (WGMn3:0) and
the Compare Output mode (COMnx1:0) bits. The Compare Output mode bits do not
affect the counting sequence, but the Waveform Generation mode bits do. The
COMnx1:0 bits control whether the PWM output generated should be inverted or not
(inverted or non-inverted PWM). For non-PWM modes the COMnx1:0 bits control if the
output should be set, cleared or toggle at a compare match (See "Compare Match
Output Unit" on page 254)
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