162
8025I–AVR–02/09
ATmega48P/88P/168P/328P
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.
15.11.3
TCNT2 – Timer/Counter Register
The Timer/Counter Register gives direct access, both for read and write operations, to the
Timer/Counter unit 8-bit counter. Writing to the TCNT2 Register blocks (removes) the Compare
Match on the following timer clock. Modifying the counter (TCNT2) while the counter is running,
introduces a risk of missing a Compare Match between TCNT2 and the OCR2x Registers.
15.11.4
OCR2A – Output Compare Register A
The Output Compare Register A contains an 8-bit value that is continuously compared with the
counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC2A pin.
15.11.5
OCR2B – Output Compare Register B
The Output Compare Register B contains an 8-bit value that is continuously compared with the
counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC2B pin.
Table 15-9.
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)
1
0
1
clk
T2S
/128 (From prescaler)
1
1
0
clk
T
2
S
/256 (From prescaler)
1
1
1
clk
T
2
S
/1024 (From prescaler)
Bit
7
6
5
4
3
2
1
0
TCNT2[7:0]
TCNT2
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
OCR2A[7:0]
OCR2A
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
OCR2B[7:0]
OCR2B
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0