Datasheet

ManualsBrandsMICROCHIP TECHNOLOGY ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller VFQFN 28 (4x4) 8-Bit 20 MHz I/O number 23

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COM2B[1] COM2B[0] Description

1 0 Clear OC0B on compare match, set OC0B at BOTTOM, (non-inverting mode)

1 1 Set OC0B on compare match, clear OC0B at BOTTOM, (inverting mode)

Note:

1. A special case occurs when OCR2B equals TOP and COM2B[1] is set. In this case, the compare

match is ignored, but the set or clear is done at TOP. Refer to 19.7.3 Fast PWM Mode for details.

The table below shows the COM2B[1:0] bit functionality when the WGM2[2:0] bits are set to phase

correct PWM mode.

Table 22-8. Compare Output Mode, Phase Correct PWM Mode

(1)

COM2B[1] COM2B[0] Description

0 0 Normal port operation, OC2B disconnected.

0 1 Reserved

1 0 Clear OC2B on compare match when up-counting. Set OC2B on compare

match when down-counting.

1 1 Set OC2B on compare match when up-counting. Clear OC2B on compare

match when down-counting.

Note:

1. A special case occurs when OCR2B equals TOP and COM2B[1] is set. In this case, the compare

match is ignored, but the set or clear is done at TOP. Refer to 22.7.4 Phase Correct PWM Mode for

details.

Bits 1:0 – WGM2[1:0] Waveform Generation Mode

Combined with the WGM2[2] bit found in the TCCR2B register, these bits control the counting sequence

of the counter, the source for maximum (TOP) counter value, and what type of waveform generation to be

used. Modes of operation supported by the Timer/Counter unit are: Normal mode (counter), Clear Timer

on Compare Match (CTC) mode, and two types of Pulse Width Modulation (PWM) modes (see 19.7

Modes of Operation).

Table 22-9. Waveform Generation Mode Bit Description

Mode

WGM2[2] WGM2[1] WGM2[0] Timer/Counter

Mode of

Operation

TOP Update of

OCR0x at

TOV Flag Set

(1)

0 0 0 0 Normal 0xFF Immediate MAX

1 0 0 1 PWM, Phase

Correct

0xFF TOP BOTTOM

2 0 1 0 CTC OCR2A Immediate MAX

3 0 1 1 Fast PWM 0xFF BOTTOM MAX

4 1 0 0 Reserved - - -

5 1 0 1 PWM, Phase

Correct

OCR2A TOP BOTTOM

6 1 1 0 Reserved - - -

7 1 1 1 Fast PWM OCR2A BOTTOM TOP

Note:

ATmega48PA/88PA/168PA

8-bit Timer/Counter2 (TC2) with PWM and A...

Datasheet Complete

DS40002011A-page 215