ATmega16A datasheet(111/352 Pages) ATMEL

111 / 352 page

111

8154B–AVR–07/09

ATmega16A

Note:

1. A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 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 101. for more details.

Table 16-4 shows the COM1x1:0 bit functionality when the WGM13:0 bits are set to the phase

correct or the phase and frequency correct, PWM mode.

Note:

1. A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 is set. See

“Phase Correct PWM Mode” on page 103. for more details.

• Bit 3 – FOC1A: Force Output Compare for Channel A

• Bit 2 – FOC1B: Force Output Compare for Channel B

The FOC1A/FOC1B bits are only active when the WGM13:0 bits specifies a non-PWM mode.

However, for ensuring compatibility with future devices, these bits must be set to zero when

TCCR1A is written when operating in a PWM mode. When writing a logical one to the

FOC1A/FOC1B bit, an immediate compare match is forced on the Waveform Generation unit.

The OC1A/OC1B output is changed according to its COM1x1:0 bits setting. Note that the

FOC1A/FOC1B bits are implemented as strobes. Therefore it is the value present in the

COM1x1:0 bits that determine the effect of the forced compare.

Table 16-3.

Compare Output Mode, Fast PWM(1)

COM1A1/COM1B1

COM1A0/COM1B0

Description

Normal port operation, OC1A/OC1B disconnected.

WGM13:0 = 15: Toggle OC1A on Compare Match,

OC1B disconnected (normal port operation).

For all other WGM13:0 settings, normal port

operation, OCnA/OCnB disconnected.

Clear OC1A/OC1B on compare match, set

OC1A/OC1B at BOTTOM,

(non-inverting mode)

Set OC1A/OC1B on compare match, clear

OC1A/OC1B at BOTTOM,

(inverting mode)

Table 16-4.

Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM

(1)

COM1A1/COM1B1

COM1A0/COM1B0

Description

Normal port operation, OC1A/OC1B disconnected.

WGM13:0 = 9 or 14: Toggle OCnA on Compare

Match, OCnB disconnected (normal port

operation).

For all other WGM13:0 settings, normal port

operation, OC1A/OC1B disconnected.

Clear OC1A/OC1B on compare match when up-

counting. Set OC1A/OC1B on compare match

when downcounting.

Set OC1A/OC1B on compare match when up-

counting. Clear OC1A/OC1B on compare match

when downcounting.

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