ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 190

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Timer/Counter Prescaler
190
ATmega640/1280/1281/2560/2561
Figure 77. Prescaler for Timer/Counter2
The clock source for Timer/Counter2 is named clk
the main system I/O clock clk
chronously 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 32.768 kHz crystal. By setting the EXCLK bit in the ASSR, a 32 KHz external
clock can be applied. See “ASSR – Asynchronous Status Register” on page 196 for
details.
For Timer/Counter2, the possible prescaled selections are: clk
clk
selected. Setting the PSRASY bit in GTCCR resets the prescaler. This allows the user
to operate with a predictable prescaler.
T2S
PSRASY
TOSC1
clk
CS20
CS21
CS22
/128, clk
AS2
I/O
T2S
/256, and clk
clk
T2S
IO
T2S
. By setting the AS2 bit in ASSR, Timer/Counter2 is asyn-
/1024. Additionally, clk
Clear
TIMER/COUNTER2 CLOCK SOURCE
0
10-BIT T/C PRESCALER
T2S
clk
. clk
T2
T2S
T2S
as well as 0 (stop) may be
is by default connected to
T2S
/8, clk
T2S
/32, clk
2549K–AVR–01/07
T2S
/64,