![](http://datasheet.mmic.net.cn/30000/MR80C32-20-D_datasheet_2377239/MR80C32-20-D_111.png)
111
8154B–AVR–07/09
ATmega16A
Note:
1. A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 is set. In
this case the compare match is ignored, but the set or clear is done at BOTTOM.
See “FastTable 16-4 shows the COM1x1:0 bit functionality when the WGM13:0 bits are set to the phase
correct or the phase and frequency correct, PWM mode.
Note:
1. A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 is set.
See Bit 3 – FOC1A: Force Output Compare for Channel A
Bit 2 – FOC1B: Force Output Compare for Channel B
The FOC1A/FOC1B bits are only active when the WGM13:0 bits specifies a non-PWM mode.
However, for ensuring compatibility with future devices, these bits must be set to zero when
TCCR1A is written when operating in a PWM mode. When writing a logical one to the
FOC1A/FOC1B bit, an immediate compare match is forced on the Waveform Generation unit.
The OC1A/OC1B output is changed according to its COM1x1:0 bits setting. Note that the
FOC1A/FOC1B bits are implemented as strobes. Therefore it is the value present in the
COM1x1:0 bits that determine the effect of the forced compare.
Table 16-3.
Compare Output Mode, Fast
PWM(1)COM1A1/COM1B1
COM1A0/COM1B0
Description
0
Normal port operation, OC1A/OC1B disconnected.
0
1
WGM13:0 = 15: Toggle OC1A on Compare Match,
OC1B disconnected (normal port operation).
For all other WGM13:0 settings, normal port
operation, OCnA/OCnB disconnected.
1
0
Clear OC1A/OC1B on compare match, set
OC1A/OC1B at BOTTOM,
(non-inverting mode)
1
Set OC1A/OC1B on compare match, clear
OC1A/OC1B at BOTTOM,
(inverting mode)
Table 16-4.
Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
COM1A1/COM1B1
COM1A0/COM1B0
Description
0
Normal port operation, OC1A/OC1B disconnected.
0
1
WGM13:0 = 9 or 14: Toggle OCnA on Compare
Match, OCnB disconnected (normal port
operation).
For all other WGM13:0 settings, normal port
operation, OC1A/OC1B disconnected.
1
0
Clear OC1A/OC1B on compare match when up-
counting. Set OC1A/OC1B on compare match
when downcounting.
1
Set OC1A/OC1B on compare match when up-
counting. Clear OC1A/OC1B on compare match
when downcounting.