ATMEGA128-16AU SL383 Atmel, ATMEGA128-16AU SL383 Datasheet - Page 106

• Manufacturer Part Number: ATMEGA128-16AU SL383
• Manufacturer: Atmel

Timer/Counter
Register – TCNT0
Output Compare
Register – OCR0
106
ATmega128
Table 55. Compare Output Mode, Phase Correct PWM Mode
Note:
• Bit 2:0 – CS02:0: Clock Select
The three clock select bits select the clock source to be used by the Timer/Counter, see
56.
Table 56. Clock Select Bit Description
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 OCR0 Register.
The Output Compare Register 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 OC0 pin.
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
COM01
CS02
0
0
1
1
0
0
0
0
1
1
1
1
1. A special case occurs when OCR0 equals TOP and COM01 is set. In this case, the compare
COM00
match is ignored, but the set or clear is done at TOP. See
101
CS01
0
1
0
1
R/W
R/W
for more details.
0
0
1
1
0
0
1
1
7
0
7
0
Description
Normal port operation, OC0 disconnected.
Reserved
Clear OC0 on compare match when up-counting. Set OC0 on compare
match when downcounting.
Set OC0 on compare match when up-counting. Clear OC0 on compare
match when downcounting.
R/W
R/W
6
0
6
0
CS00
0
1
0
1
0
1
0
1
R/W
R/W
5
0
5
0
Description
No clock source (Timer/Counter stopped)
clk
clk
clk
clk
clk
clk
clk
T
T
T0S
T0S
T0S
T0S
T0S
0
0
S
S
/256 (From prescaler)
/1024 (From prescaler)
R/W
R/W
/(No prescaling)
/8 (From prescaler)
/32 (From prescaler)
/64 (From prescaler)
/128 (From prescaler)
4
0
4
0
TCNT0[7:0]
OCR0[7:0]
R/W
R/W
3
0
3
0
R/W
R/W
2
0
2
0
(1)
“Phase Correct PWM Mode” on page
R/W
R/W
1
0
1
0
R/W
R/W
0
0
0
0
TCNT0
OCR0
2467S–AVR–07/09
Table