ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 156

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

18.11.2
18.11.3
8285D–AVR–06/11
TCNT2 – Timer/Counter Register
OCR2A – Output Compare Register A
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
• Bit 2:0 – CS2[2:0]: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter, see
18-6.
Table 18-6.
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 OCR2A Register.
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.
Bit
(0xB2)
Read/Write
Initial Value
Bit
(0xB3)
Read/Write
Initial Value
CS22
0
0
0
0
1
1
1
1
Clock Select Bit Description
R/W
R/W
7
0
7
0
CS21
0
0
1
1
0
0
1
1
R/W
R/W
6
0
6
0
CS20
R/W
R/W
0
1
0
1
0
1
0
1
5
0
5
0
R/W
R/W
Description
No clock source (Timer/Counter stopped).
clk
clk
clk
clk
clk
clk
clk
4
0
4
0
OCR2A[7:0]
TCNT2[7:0]
T2S
T2S
T2S
T2S
T2S
T
T
2
2
S
S
/256 (From prescaler)
/1024 (From prescaler)
/(No prescaling)
/8 (From prescaler)
/32 (From prescaler)
/64 (From prescaler)
/128 (From prescaler)
R/W
R/W
3
0
3
0
R/W
R/W
2
0
2
0
R/W
R/W
1
0
1
0
R/W
R/W
0
0
0
0
TCNT2
OCR2A
Table
156