TCCR0 – Timer/Counter Control Register

When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When addressing I/O Registers as data space using LD and ST instructions, 0x20 must be added to these offset addresses.

Name:
TCCR0
Offset:
0x33 [ID-000004b0]
Reset:
0
Access:
When addressing I/O registers as data space the offset address is 0x53
Bit76543210
CS0n[2:0]
AccessR/WR/WR/W
Reset000

Bits 2:0 – CS0n: Clock Select [n = 2:0]

Clock Select [n = 2:0]

The three clock select bits select the clock source to be used by the Timer/Counter.

CS02 CS01 CS00 Description
0 0 0 No clock source (Timer/Counter stopped).
0 0 1 clkI/O/(No prescaling)
0 1 0 clkI/O/8 (From prescaler)
0 1 1 clkI/O/64 (From prescaler)
1 0 0 clkI/O/256 (From prescaler)
1 0 1 clkI/O/1024 (From prescaler)
1 1 0 External clock source on T0 pin. Clock on falling edge.
1 1 1 External clock source on T0 pin. Clock on rising edge.

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.