Datasheet

CA22 CA21 CS20 Description
0 1 1 clk
I/O
/32 (From prescaler)
1 0 0 clkI/O/64 (From prescaler)
1 0 1 clk
I/O
/128 (From prescaler)
1 1 0 clk
I/O
/256 (From prescaler)
1 1 1 clk
I/O
/1024 (From prescaler)
If external pin modes are used for the Timer/Counter0, transitions on the T0 pin will clock the counter
even if the pin is configured as an output. This feature allows software control of the counting.
Atmel ATmega644A [DATASHEET]
Atmel-42716C-ATmega644A_Datasheet_Complete-10/2016
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