ATmega328P datasheet(109/448 Pages) ATMEL

109 / 448 page

109

8161D–AVR–10/09

ATmega48PA/88PA/168PA/328P

14.9.2

TCCR0B – Timer/Counter Control Register B

• Bit 7 – FOC0A: Force Output Compare A

The FOC0A bit is only active when the WGM bits specify a non-PWM mode.

However, for ensuring compatibility with future devices, this bit must be set to zero when

TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0A bit,

an immediate Compare Match is forced on the Waveform Generation unit. The OC0A output is

changed according to its COM0A1:0 bits setting. Note that the FOC0A bit is implemented as a

strobe. Therefore it is the value present in the COM0A1:0 bits that determines the effect of the

forced compare.

A FOC0A strobe will not generate any interrupt, nor will it clear the timer in CTC mode using

OCR0A as TOP.

The FOC0A bit is always read as zero.

• Bit 6 – FOC0B: Force Output Compare B

The FOC0B bit is only active when the WGM bits specify a non-PWM mode.

However, for ensuring compatibility with future devices, this bit must be set to zero when

TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0B bit,

an immediate Compare Match is forced on the Waveform Generation unit. The OC0B output is

changed according to its COM0B1:0 bits setting. Note that the FOC0B bit is implemented as a

strobe. Therefore it is the value present in the COM0B1:0 bits that determines the effect of the

forced compare.

A FOC0B strobe will not generate any interrupt, nor will it clear the timer in CTC mode using

OCR0B as TOP.

The FOC0B bit is always read as zero.

• Bits 5:4 – Res: Reserved Bits

These bits are reserved bits in the ATmega48PA/88PA/168PA/328P and will always read as

zero.

• Bit 3 – WGM02: Waveform Generation Mode

See the description in the ”TCCR0A – Timer/Counter Control Register A” on page 106.

• Bits 2:0 – CS02:0: Clock Select

The three Clock Select bits select the clock source to be used by the Timer/Counter.

Bit

0x25 (0x45)

FOC0A

FOC0B

–

WGM02

CS02

CS01

CS00

TCCR0B

Read/Write

R/W

Initial Value

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