ATMEGA16-16AU SL602 Atmel, ATMEGA16-16AU SL602 Datasheet - Page 134

• Manufacturer Part Number: ATMEGA16-16AU SL602
• Manufacturer: Atmel

Timer/Counter
Prescaler
Special Function IO
Register – SFIOR
2466T–AVR–07/10
Figure 64. 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 32.768 kHz crystal. Apply-
ing an external clock source to TOSC1 is not recommended.
For Timer/Counter2, the possible prescaled selections are: clk
clk
Setting the PSR2 bit in SFIOR resets the prescaler. This allows the user to operate with a pre-
dictable prescaler.
• Bit 1 – PSR2: Prescaler Reset Timer/Counter2
When this bit is written to one, the Timer/Counter2 prescaler will be reset. The bit will be cleared
by hardware after the operation is performed. Writing a zero to this bit will have no effect. This bit
will always be read as zero if Timer/Counter2 is clocked by the internal CPU clock. If this bit is
written when Timer/Counter2 is operating in asynchronous mode, the bit will remain one until the
prescaler has been reset.
Bit
Read/Write
Initial Value
T2S
/128, clk
TOSC1
clk
PSR2
CS20
CS21
CS22
AS2
I/O
ADTS2
R/W
T2S
7
0
/256, and clk
ADTS1
IO
R/W
. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously
6
0
clk
T2S
ADTS0
T2S
R/W
5
0
/1024. Additionally, clk
Clear
R
4
–
0
TIMER/COUNTER2 CLOCK SOURCE
ACME
R/W
0
T2S
3
0
. clk
10-BIT T/C PRESCALER
T2S
clk
T2S
PUD
R/W
T2
2
0
as well as 0 (stop) may be selected.
is by default connected to the main
PSR2
R/W
1
0
T2S
ATmega16(L)
/8, clk
PSR10
R/W
0
0
T2S
/32, clk
SFIOR
T2S
/64,
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