Datasheet

163
ATmega640/1280/1281/2560/2561
2549K–AVR–01/07
• Bit 2:0 – CSn2:0: Clock Select
The three clock select bits select the clock source to be used by the Timer/Counter, see
Figure 57 and Figure 58.
If external pin modes are used for the Timer/Countern, transitions on the Tn pin will
clock the counter even if the pin is configured as an output. This feature allows software
control of the counting.
Table 86. Clock Select Bit Description
CSn2 CSn1 CSn0 Description
000No clock source. (Timer/Counter stopped)
001clk
I/O
/1 (No prescaling
010clk
I/O
/8 (From prescaler)
011clk
I/O
/64 (From prescaler)
100clk
I/O
/256 (From prescaler)
101clk
I/O
/1024 (From prescaler)
1 1 0 External clock source on Tn pin. Clock on falling edge
1 1 1 External clock source on Tn pin. Clock on rising edge