ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 153

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

18.10 Timer/Counter Prescaler
8285D–AVR–06/11
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
Figure 18-12. Prescaler for Timer/Counter2
The clock source for Timer/Counter2 is named clk
system I/O clock clk
clocked from the TOSC1 pin. This enables use of Timer/Counter2 as a Real Time Counter
(RTC). When AS2 is set, pins TOSC1 and TOSC2 are disconnected from Port C. A crystal can
then be connected between the TOSC1 and TOSC2 pins to serve as an independent clock
source for Timer/Counter2. The Oscillator is optimized for use with a 32.768kHz crystal. If apply-
ing an external clock on TOSC1, the EXCLK bit in ASSR must be set.
For Timer/Counter2, the possible prescaled selections are: clk
clk
Setting the PSR2 bit in GTCCR resets the prescaler. This allows the user to operate with a pre-
dictable prescaler.
T2S
/128, clk
TOSC1
clk
PSR2
CS20
CS21
CS22
AS2
I/O
T2S
/256, and clk
IO
. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously
clk
T2S
T2S
/1024. Additionally, clk
Clear
TIMER/COUNTER2 CLOCK SOURCE
T2S
0
. clk
10-BIT T/C PRESCALER
T2S
clk
T2S
T2
as well as 0 (stop) may be selected.
is by default connected to the main
T2S
/8, clk
T2S
/32, clk
T2S
/64,
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