![](http://datasheet.mmic.net.cn/Atmel/AT32AP7000-CTUR_datasheet_96418/AT32AP7000-CTUR_105.png)
105
2545T–AVR–05/11
ATmega48/88/168
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.
15.9.3
TCNT0 – 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 TCNT0 Register blocks (removes) the Compare
Match on the following timer clock. Modifying the counter (TCNT0) while the counter is running,
introduces a risk of missing a Compare Match between TCNT0 and the OCR0x Registers.
15.9.4
OCR0A – Output compare register A
The Output Compare Register A contains an 8-bit value that is continuously compared with the
counter value (TCNT0). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC0A pin.
15.9.5
OCR0B – Output compare register B
The Output Compare Register B contains an 8-bit value that is continuously compared with the
counter value (TCNT0). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC0B pin.
Table 15-9.
Clock select bit description.
CS02
CS01
CS00
Description
0
No clock source (timer/counter stopped)
00
1
clkI/O/(no prescaling)
01
0
clkI/O/8 (from prescaler)
01
1
clkI/O/64 (from prescaler)
10
0
clkI/O/256 (from prescaler)
10
1
clkI/O/1024 (from prescaler)
1
0
External clock source on T0 pin. Clock on falling edge.
1
External clock source on T0 pin. Clock on rising edge.
Bit
7
654
32
10
TCNT0[7:0]
TCNT0
Read/write
R/W
Initial value
0
Bit
7
654
32
10
OCR0A[7:0]
OCR0A
Read/write
R/W
Initial value
0
Bit
7
654
32
10
OCR0B[7:0]
OCR0B
Read/write
R/W
Initial value
0