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Timer/Counters
The ATtiny15L provides two general-purpose 8-bit Timer/Counters. The Timer/Counters have separate prescaling selec-
tion from separate 10-bit prescalers. The Timer/Counter0 uses internal clock (CK) as the clock timebase. The
Timer/Counter1 may use either the internal clock (CK) or the fast peripheral clock (PCK) as the clock time base.
The Timer/Counter0 Prescaler
Figure below shows the Timer/Counter prescaler.
Figure 18. Timer/Counter0 Prescaler
The four 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. Setting the PSR10 bit in SFIOR resets the prescaler. This allows
the user to operate with a predictable prescaler.
The Timer/Counter1 Prescaler
Figure 19 shows the Timer/Counter1 prescaler. For Timer/Counter1 the clock selections are: PCK, PCK/2, PCK/4, PCK/8,
CK (=PCK/16), CK/2, CK/4, CK/8,CK/16, CK/32, CK/64, CK/128, CK/256, CK/512, CK/1024, and stop. The clock options
are described in Table 12 on page 30 and the Timer/Counter1 Control Register, TCCR1. Setting the PSR1 bit in the SFIOR
register resets the 10-bit prescaler. This allows the user to operate with a predictable prescaler.
24
CK
CLEAR
PSR0
T0
CS00
CS01
CS02
ATtiny15L
10-BIT T/C PRESCALER
0
TIMER/COUNTER0 CLOCK SOURCE
TCK0
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