ATmega1284P datasheet(104/380 Pages) ATMEL

104 / 380 page

104

8059D–AVR–11/09

ATmega1284P

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 100 for more details.

• Bits 5:4 – COM0B1:0: Compare Match Output B Mode

These bits control the Output Compare pin (OC0B) behavior. If one or both of the COM0B1:0

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 COM0B1:0 bits depends on the

WGM02:0 bit setting. Table 13-2 on page 103 shows the COM0A1:0 bit functionality when the

WGM02:0 bits are set to a normal or CTC mode (non-PWM).

Table 13-6 shows the COM0B1:0 bit functionality when the WGM02:0 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 atBOTTOM. See ”Fast PWM Mode” on page

98 for more details.

Table 13-4.

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 13-5.

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 13-6.

Compare Output Mode, Fast PWM Mode(1)

COM0B1

COM0B0

Description

Normal port operation, OC0B disconnected.

Reserved

Clear OC0B on Compare Match, set OC0B at BOTTOM,

(non-inverting mode).

Set OC0B on Compare Match, clear OC0B at BOTTOM,

(inverting mode).

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