ATmega16U4 datasheet(165/408 Pages) ATMEL

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7766D–AVR–01/09

ATmega16U4/ATmega32U4

that the Data Direction Register (DDR) bit corresponding to the OC4B pin must be set in order to

enable the output driver.

The function of the COM4B1:0 bits depends on the PWM4B and WGM40 bit settings. Table 15-

11 shows the COM4B1:0 bit functionality when the PWM4B bit is set to Normal Mode (non-

PWM).

Table 15-12 shows the COM4B1:0 bit functionality when the PWM4B and WGM40 bits are set to

Fast PWM Mode.

Table 15-13 shows the COM4B1:0 bit functionality when the PWM4B and WGM40 bits are set to

Phase and Frequency Correct PWM Mode.

• Bit 3 - FOC4A: Force Output Compare Match 4A

The FOC4A bit is only active when the PWM4A bit specify a non-PWM mode.

Writing a logical one to this bit forces a change in the Waveform Output (OCW4A) and the Out-

put Compare pin (OC4A) according to the values already set in COM4A1 and COM4A0. If

COM4A1 and COM4A0 written in the same cycle as FOC4A, the new settings will be used. The

Force Output Compare bit can be used to change the output pin value regardless of the timer

Table 15-11. Compare Output Mode, Normal Mode (non-PWM)

COM4B1..0

OCW4B Behavior

OC4B Pin

Normal port operation.

Disconnected

Toggle on Compare Match.

Connected

Disconnected

Clear on Compare Match.

Connected

Disconnected

Set on Compare Match.

Connected

Disconnected

Table 15-12. Compare Output Mode, Fast PWM Mode

COM4B1..0

OCW4B Behavior

OC4B Pin

Normal port operation.

Disconnected

Cleared on Compare Match.

Set when TCNT4 = 0x000.

Connected

Cleared on Compare Match.

Set when TCNT4 = 0x000.

Connected

Disconnected

Set on Compare Match.

Cleared when TCNT4 = 0x000.

Connected

Disconnected

Table 15-13. Compare Output Mode, Phase and Frequency Correct PWM Mode

COM4B1..0

OCW4B Behavior

OC4B Pin

Normal port operation.

Disconnected

Cleared on Compare Match when up-counting.

Set on Compare Match when down-counting.

Connected

Cleared on Compare Match when up-counting.

Set on Compare Match when down-counting.

Connected

Disconnected

Set on Compare Match when up-counting.

Cleared on Compare Match when down-counting.

Connected

Disconnected

ATmega16U4 Datasheet(PDF) 165 Page - ATMEL Corporation

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