Datasheet

ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
90
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.
12.8.3 Timer/Counter Register – TCNT0
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.
12.8.4 Output Compare Register A – OCR0A
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.
12.8.5 Output Compare Register B – OCR0B
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 12-9. Clock Select Bit Description
CS02 CS01 CS00 Description
0 0 0 No clock source (Timer/Counter stopped)
0 0 1 clk
I/O
/(no prescaling)
0 1 0 clk
I/O
/8 (from prescaler)
0 1 1 clk
I/O
/64 (from prescaler)
1 0 0 clk
I/O
/256 (from prescaler)
1 0 1 clk
I/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.
Bit 76543210
TCNT0[7:0] TCNT0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
Bit 76543210
OCR0A[7:0] OCR0A
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
Bit 76543210
OCR0B[7:0] OCR0B
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000