Datasheet

Table Of Contents
79
ATmega32A [DATASHEET]
Atmel-8155D-AVR-ATmega32A-Datasheet_02/2014
Note: 1. The CTC0 and PWM0 bit definition names are now obsolete. Use the WGM01:0 definitions. However, the function-
ality and location of these bits are compatible with previous versions of the timer.
Bit 5:4 – COM0[1:0]: Compare Match Output Mode
These bits control the Output Compare pin (OC0) behavior. If one or both of the COM01:0 bits are set, the OC0
output overrides the normal port functionality of the I/O pin it is connected to. However, note that the Data Direction
Register (DDR) bit corresponding to the OC0 pin must be set in order to enable the output driver.
When OC0 is connected to the pin, the function of the COM01:0 bits depends on the WGM01:0 bit setting. Table
14-3 shows the COM01:0 bit functionality when the WGM01:0 bits are set to a normal or CTC mode (non-PWM).
Table 14-4 shows the COM01:0 bit functionality when the WGM01:0 bits are set to fast PWM mode.
Note: 1. A special case occurs when OCR0 equals TOP and COM01 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 79 for more details.
Table 14-5 shows the COM0[1:0] bit functionality when the WGM01:0 bits are set to phase correct PWM mode.
Note: 1. A special case occurs when OCR0 equals TOP and COM01 is set. In this case, the compare match is ignored, but
the set or clear is done at TOP. See “Phase Correct PWM Mode” on page 80 for more details.
Bit 2:0 – CS02:0: Clock Select
Table 15-3. Compare Output Mode, non-PWM Mode
COM01 COM00 Description
0 0 Normal port operation, OC0 disconnected.
0 1 Toggle OC0 on compare match
1 0 Clear OC0 on compare match
1 1 Set OC0 on compare match
Table 15-4. Compare Output Mode, Fast PWM Mode
(1)
COM01 COM00 Description
0 0 Normal port operation, OC0 disconnected.
01Reserved
1 0 Clear OC0 on compare match, set OC0 at BOTTOM,
(nin-inverting mode)
1 1 Set OC0 on compare match, clear OC0 at BOTTOM,
(inverting mode)
Table 15-5. Compare Output Mode, Phase Correct PWM Mode
(1)
COM01 COM00 Description
0 0 Normal port operation, OC0 disconnected.
01Reserved
1 0 Clear OC0 on compare match when up-counting. Set OC0 on compare match
when downcounting.
1 1 Set OC0 on compare match when up-counting. Clear OC0 on compare match
when downcounting.