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ATMEGA48V_11 Datasheet, PDF (105/377 Pages) ATMEL Corporation – 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
ATmega48/88/168
Table 15-9. Clock select bit description.
CS02 CS01 CS00 Description
0
0
0 No clock source (timer/counter stopped)
0
0
1
clkI/O/(no prescaling)
0
1
0
clkI/O/8 (from prescaler)
0
1
1
clkI/O/64 (from prescaler)
1
0
0
clkI/O/256 (from prescaler)
1
0
1
clkI/O/1024 (from prescaler)
1
1
0 External clock source on T0 pin. Clock on falling edge.
1
1
1 External clock source on T0 pin. Clock on rising edge.
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
Bit
0x26 (0x46)
Read/write
Initial value
7
6
5
4
3
2
1
0
TCNT0[7:0]
TCNT0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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
Bit
0x27 (0x47)
Read/write
Initial value
7
6
5
4
3
2
1
0
OCR0A[7:0]
OCR0A
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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
Bit
0x28 (0x48)
Read/write
Initial value
7
6
5
4
3
2
1
0
OCR0B[7:0]
OCR0B
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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.
2545T–AVR–05/11
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