Datasheet

Table Of Contents
Table 19-3. Compare Output Mode, Fast PWM
(1)
COM1A1/
COM1B1
COM1A0/
COM1B0
Description
0 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 WGM1
settings, normal port operation, OC1A/OC1B disconnected.
1 0 Clear OC1A/OC1B on Compare Match, set OC1A/OC1B at
BOTTOM (non-inverting mode)
1 1 Set OC1A/OC1B on Compare Match, clear OC1A/OC1B at
BOTTOM (inverting mode)
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. Refer to Fast PWM Mode
for details.
The table below 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.
Table 19-4. Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
(1)
COM1A1/
COM1B1
COM1A0/
COM1B0
Description
0 0 Normal port operation, OC1A/OC1B disconnected.
0 1 WGM13:0 = 9 or 14: Toggle OC1A on Compare Match, OC1B
disconnected (normal port operation). For all other WGM1 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 down-counting.
1 1 Set OC1A/OC1B on Compare Match when up-counting. Clear
OC1A/OC1B on Compare Match when down-counting.
Note:  1. A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 is set. Refer
to Phase Correct PWM Mode for details.
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.
A FOC1A/FOC1B strobe will not generate any interrupt nor will it clear the timer in Clear Timer on
Compare Match (CTC) mode using OCR1A as TOP.
The FOC1A/FOC1B bits are always read as zero.
Atmel ATmega32A [DATASHEET]
Atmel-8155I-ATmega32A_Datasheet_Complete-08/2016
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