21.11.2 TC2 Control Register B

Name: TCCR2B
Offset: 0xB1
Reset: 0x00
Property: -

Bit 76543210 
 FOC2AFOC2B   WGM2 [2]CS2[2:0] 
Access R/WR/WR/WR/WR/WR/W 
Reset 000000 

Bit 7 – FOC2A Force Output Compare A

The FOC2A bit is only active when the WGM bits specify a non-PWM mode.

To ensure compatibility with future devices, this bit must be set to zero when TCCR2B is written when operating in PWM mode. When writing a logical one to the FOC2A bit, an immediate Compare Match is forced on the Waveform Generation unit. The OC2A output is changed according to its COM2A[1:0] bits setting. Note that the FOC2A bit is implemented as a strobe. Therefore it is the value present in the COM2A[1:0] bits that determines the effect of the forced compare.

A FOC2A strobe will not generate any interrupt, nor will it clear the timer in CTC mode using OCR2A as TOP.

The FOC2A bit is always read as zero.

Bit 6 – FOC2B  Force Output Compare B

The FOC2B bit is only active when the WGM bits specify a non-PWM mode.

To ensure compatibility with future devices, this bit must be set to zero when TCCR2B is written when operating in PWM mode. When writing a logical one to the FOC2B bit, an immediate Compare Match is forced on the Waveform Generation unit. The OC2B output is changed according to its COM2B[1:0] bits setting. Note that the FOC2B bit is implemented as a strobe. Therefore it is the value present in the COM2B[1:0] bits that determines the effect of the forced compare.

A FOC2B strobe will not generate any interrupt, nor will it clear the timer in CTC mode using OCR2B as TOP.

The FOC2B bit is always read as zero.

Bit 3 – WGM2 [2] Waveform Generation Mode

Refer to TCCR2A.

Bits 2:0 – CS2[2:0] Clock Select 2 [n = 0..2]

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

Table 21-10. Clock Select Bit Description
CS22CS21CS20Description
000No clock source (Timer/Counter stopped).
001clkI/O/1 (No prescaling)
010clkI/O/8 (From prescaler)
011clkI/O/32 (From prescaler)
100clkI/O/64 (From prescaler)
101clkI/O/128 (From prescaler)
110clkI/O/256 (From prescaler)
111clkI/O/1024 (From prescaler)

If external pin modes are used for the Timer/Counter0, transitions on the T0 pin will clock the counter even if the pin is configured as an output. This feature allows software control of the counting.