Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI Data Sheet
Product codes
MEGA328P-XMINI
157
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
Atmel-8271H-AVR- ATmega-Datasheet_08/2014
18.11.2 TCCR2B – Timer/Counter Control Register B
• Bit 7 – FOC2A: Force Output Compare A
The FOC2A 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 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 COM2A1:0 bits setting.
Note that the FOC2A bit is implemented as a strobe. Therefore it is the value present in the COM2A1:0 bits that
determines the effect of the forced compare.
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 COM2A1:0 bits setting.
Note that the FOC2A bit is implemented as a strobe. Therefore it is the value present in the COM2A1:0 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.
However, for ensuring 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 COM2B1:0 bits setting.
Note that the FOC2B bit is implemented as a strobe. Therefore it is the value present in the COM2B1:0 bits that
determines the effect of the forced compare.
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 COM2B1:0 bits setting.
Note that the FOC2B bit is implemented as a strobe. Therefore it is the value present in the COM2B1:0 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.
• Bits 5:4 – Reserved
These bits are reserved bits in the ATmega48A/PA/88A/PA/168A/PA/328/P and will always read as zero.
• Bit 3 – WGM22: Waveform Generation Mode
• Bit 2:0 – CS22:0: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter, see
Bit
7
6
5
4
3
2
1
0
FOC2A
FOC2B
–
–
WGM22
CS22
CS21
CS20
TCCR2B
Read/Write
W
W
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Table 18-9.
Clock Select Bit Description
CS22
CS21
CS20
Description
0
0
0
No clock source (Timer/Counter stopped).
0
0
1
clk
T2S
/(No prescaling)
0
1
0
clk
T2S
/8 (From prescaler)
0
1
1
clk
T2S
/32 (From prescaler)
1
0
0
clk
T2S
/64 (From prescaler)