ATmega32U2 datasheet(103/314 Pages) ATMEL

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103

7799B–AVR–07/09

ATmega8U2/16U2/32U2

Table 15-4 shows the COM0A1:0 bit functionality when the WGM0[2:0] bits are set to phase cor-

rect PWM mode.

Note:

1. A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case, the Com-

pare Match is ignored, but the set or clear is done at TOP. See “Phase Correct PWM Mode” on

page 99 for more details.

• Bits 5:4 – COM0B[1:0]: Compare Match Output B Mode

These bits control the Output Compare pin (OC0B) behavior. If one or both of the COM0B[1:0]

bits are set, the OC0B 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 OC0B pin

must be set in order to enable the output driver.

When OC0B is connected to the pin, the function of the COM0B[1:0] bits depends on the

WGM0[2:0] bit setting. Table 15-2 shows the COM0A[1:0] bit functionality when the WGM0[2:0]

bits are set to a normal or CTC mode (non-PWM).

[

Table 15-3 shows the COM0B[1:0] bit functionality when the WGM0[2:0] bits are set to fast

PWM mode.

Note:

1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the Com-

pare Match is ignored, but the set or clear is done at TOP. See “Fast PWM Mode” on page 97

for more details.

Table 15-4.

Compare Output Mode, Phase Correct PWM Mode(1)

COM0A1

COM0A0

Description

Normal port operation, OC0A disconnected.

WGM02 = 0: Normal Port Operation, OC0A Disconnected.

WGM02 = 1: Toggle OC0A on Compare Match.

Clear OC0A on Compare Match when up-counting. Set OC0A on

Compare Match when down-counting.

Set OC0A on Compare Match when up-counting. Clear OC0A on

Compare Match when down-counting.

Table 15-5.

Compare Output Mode, non-PWM Mode

COM0B1

COM0B0

Description

Normal port operation, OC0B disconnected.

Toggle OC0B on Compare Match

Clear OC0B on Compare Match

Set OC0B on Compare Match

Table 15-6.

Compare Output Mode, Fast PWM Mode

(1)

COM0B1

COM0B0

Description

Normal port operation, OC0B disconnected.

Reserved

Clear OC0B on Compare Match, set OC0B at TOP

Set OC0B on Compare Match, clear OC0B at TOP

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