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ATtiny22/22L
Timer/Counter
The ATtiny22/L provides one general purpose 8- bit Timer/Counter - Timer/Counter0. The Timer/Counter has prescaling
selection from the 10-bit prescaling timer. The Timer/Counter can either be used as a timer with an internal clock timebase
or as a counter with an external pin connection that triggers the counting.
Timer/Counter Prescaler
Figure 27 shows the Timer/Counter prescaler.
Figure 27. Timer/Counter0 Prescaler
The four different prescaled selections are: CK/8, CK/64, CK/256 and CK/1024 where CK is the oscillator clock. CK,
external source and stop, can also be selected as clock sources.
8-Bit Timer/Counter0
Figure 28 shows the block diagram for Timer/Counter0.
The 8-bit Timer/Counter0 can select clock source from CK, prescaled CK, or an external pin. In addition, it can be stopped
as described in the specification for the Timer/Counter0 Control Register - TCCR0. The overflow status flag is found in the
Timer/Counter Interrupt Flag Register - TIFR. Control signals are found in the Timer/Counter0 Control Register - TCCR0.
The interrupt enable/disable settings for Timer/Counter0 are found in the Timer/Counter Interrupt Mask Register - TIMSK.
When Timer/Counter0 is externally clocked, the external signal is synchronized with the oscillator frequency of the CPU. To
ensure proper sampling of the external clock, the minimum time between two external clock transitions must be at least one
internal CPU clock period. The external clock signal is sampled on the rising edge of the internal CPU clock.
The 8-bit Timer/Counter0 features both a high resolution and a high accuracy usage with the lower prescaling opportuni-
ties. Similarly, the high prescaling opportunities make the Timer/Counter0 useful for lower speed functions or exact timing
functions with infrequent actions.
10-BIT T/C PRESCALER
0
TIMER/COUNTER0 CLOCK SOURCE
TCK0
CK
T0
CS00
CS01
CS02
CK/8
CK/256
CK/1024
CK/64
