atmega323l ATMEL Corporation, atmega323l Datasheet - Page 43

• Manufacturer Part Number: atmega323l
• Description: Atmega323 8-bit Avr Microcontroller With 32k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Timer/Counters
Timer/Counter
Prescalers
1457G–AVR–09/03
The ATmega323 provides three general purpose Timer/Counters – two 8-bit T/Cs and
one 16-bit T/C. Timer/Counter2 can optionally be asynchronously clocked from an exter-
nal Oscillator. This Oscillator is optimized for use with a 32.768 kHz watch crystal,
enabling use of Timer/Counter2 as a Real Time Counter (RTC). Timer/Counters 0 and 1
have individual prescaling selection from the same 10-bit prescaler. Timer/Counter2 has
its own prescaler. Both these prescalers can be reset by setting the corresponding con-
trol bits in the Special Functions IO Register (SFIOR). These Timer/Counters can either
be used as a timer with an internal clock time-base or as a counter with an external pin
connection which triggers the counting.
Figure 30. Prescaler for Timer/Counter0 and Timer/Counter1
For Timer/Counters 0 and 1, the four different prescaled selections are: CK/8, CK/64,
CK/256, and CK/1024, where CK is the Oscillator clock. For the two Timer/Counters0
and 1, CK, external source, and stop can also be selected as clock sources. Setting the
PSR10 bit in SFIOR Resets the prescaler. This allows the user to operate with a predict-
able prescaler. Note that Timer/Counter1 and Timer/Counter0 share the same prescaler
and a Prescaler Reset will affect both Timer/Counters.
PSR10
TCK1
Clear
ATmega323(L)
TCK0
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