ATmega644PA datasheet(135/468 Pages) ATMEL

135 / 468 page

135

8152G–AVR–11/09

ATmega164PA/324PA/644PA/1284P

Table 15-3 on page 135 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to

the fast PWM mode.

Note:

1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is set. In

this case the compare match is ignored, but the set or clear is done at BOTTOM. See Section

“15.9.3” on page 126. for more details.

Table 15-4 on page 135 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to

the phase correct or the phase and frequency correct, PWM mode.

Note:

1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is set. See

Section “15.9.4” on page 128. for more details.

• Bit 1:0 – WGMn1:0: Waveform Generation Mode

Combined with the WGMn3:2 bits found in the TCCRnB Register, these bits control the counting

sequence of the counter, the source for maximum (TOP) counter value, and what type of wave-

form generation to be used, see Table 15-5 on page 136. Modes of operation supported by the

Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare match (CTC) mode,

and three types of Pulse Width Modulation (PWM) modes. (See Section “15.9” on page 125.).

Table 15-3.

Compare Output Mode, Fast PWM

(1)

COMnA1/COMnB1

COMnA0/COMnB0

Description

Normal port operation, OCnA/OCnB disconnected.

WGMn3:0 = 14 or 15: Toggle OC1A on Compare

Match, OC1B disconnected (normal port operation).

For all other WGM1 settings, normal port operation,

OC1A/OC1B disconnected.

Clear OCnA/OCnB on Compare Match, set

OCnA/OCnB at BOTTOM (non-inverting mode)

Set OCnA/OCnB on Compare Match, clear

OCnA/OCnB at BOTTOM (inverting mode)

Table 15-4.

Compare Output Mode, Phase Correct and Phase and Frequency Correct

PWM(1)

COMnA1/COMnB1

COMnA0/COMnB0

Description

Normal port operation, OCnA/OCnB disconnected.

WGMn3:0 = 9 or 11: Toggle OCnA on Compare

Match, OCnB disconnected (normal port operation).

For all other WGM1 settings, normal port operation,

OC1A/OC1B disconnected.

Clear OCnA/OCnB on Compare Match when up-

counting. Set OCnA/OCnB on Compare Match when

downcounting.

Set OCnA/OCnB on Compare Match when up-

counting. Clear OCnA/OCnB on Compare Match

when downcounting.

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