ATtiny15L
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Bits 3,2,1,0 - CS13, CS12, CS11, CS10: Clock Select bits 3, 2, 1, and 0
The Clock Select bits 3, 2, 1, and 0 define the prescaling source of Timer/Counter1.
The Stop condition provides a Timer Enable/Disable function. The prescaled CK modes are scaled directly from the CK
oscillator clock.
The Timer/Counter1 – TCNT1
This 8-bit register contains the value of Timer/Counter1.
Timer/Counter1 is implemented as an up-counter with read and write access. Due to synchronization of the CPU and
Timer/Counter1, data written into Timer/Counter1 is delayed by one CPU clock cycle.
Timer/Counter1 Output Compare RegisterA – OCR1A
The Output Compare Register 1A is an 8-bit read/write register.
The Timer/Counter Output Compare Register 1A contains the data to be continuously compared with Timer/Counter1.
Actions on compare matches are specified in TCCR1. A compare match does only occur if Timer/Counter1 counts to the
OCR1A value. A software write that sets TCNT1 and OCR1A to the same value does not generate a compare match.
A compare match will set (one) the compare interrupt flag in the CPU clock cycle following the compare event.
Table 11.
Timer/Counter1 Prescale Select
CS13
CS12
CS11
CS10
Description
0
0
0
0
Timer/Counter1 is stopped.
0
0
0
1
CK*16 (=PCK)
0
0
1
0
CK*8 (=PCK/2)
0
0
1
1
CK*4 (=PCK/4)
0
1
0
0
CK*2 (=PCK/8)
0
1
0
1
CK
0
1
1
0
CK/2
0
1
1
1
CK/4
1
0
0
0
CK/8
1
0
0
1
CK/16
1
0
1
0
CK/32
1
0
1
1
CK/64
1
1
0
0
CK/128
1
1
0
1
CK/256
1
1
1
0
CK/512
1
1
1
1
CK/1024
Bit
7
6
5
4
3
2
1
0
$2F
MSB
LSB
TCNT1
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
$2E
MSB
LSB
OCR1A
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
