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Timer/Counters
The Timer/Counter0
Prescaler
The Timer/Counter1
Prescaler
1187H–AVR–09/07
The ATtiny15L provides two general purpose 8-bit Timer/Counters. The Timer/Counters
have sepa ra te pr es caling selection from separate 10-bit prescalers. The
Timer/Counter0 uses internal clock (CK) as the clock time base. The Timer/Counter1
may use either the internal clock (CK) or the fast peripheral clock (PCK) as the clock
time base.
Figure 18 shows the Timer/Counter prescaler.
Figure 18. Timer/Counter0 Prescaler
CK
PSR0
T0
CS00
CS01
CS02
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.
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 31 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 oper-
ate with a predictable prescaler.
Figure 19. Timer/Counter1 Prescaler
CK
(1.6 MHz)
PSR1
PCK
3-BIT T/C PRESCALER
(25.6 MHz)
CS10
CS11
CS12
CS13
10-BIT T/C PRESCALER
CLEAR
0
TIMER/COUNTER0 CLOCK SOURCE
TCK0
10-BIT T/C PRESCALER
CLEAR
CLEAR
0
TIMER/COUNTER1 CLOCK SOURCE
ATtiny15L
25
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