ATTINY15 ATMEL [ATMEL Corporation], ATTINY15 Datasheet - Page 31

• Manufacturer Part Number: ATTINY15
• Manufacturer: ATMEL [ATMEL Corporation]

The Timer/Counter1 – TCNT1
Timer/Counter1 Output
Compare RegisterA – OCR1A
Timer/Counter1 in PWM Mode
1187D–12/01
Table 11. Timer/Counter1 Prescale Select (Continued)
The Stop condition provides a Timer Enable/Disable function. The prescaled CK modes
are scaled directly from the CK oscillator clock.
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.
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 occurs only 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 follow-
ing the compare event.
When the PWM mode is selected, Timer/Counter1 and the Output Compare Register A
(OCR1A) form an 8-bit, free-running and glitch-free PWM with outputs on the
PB1(OC1A) pin. Timer/Counter1 acts as an up-counter, counting up from $00 up to the
value specified in the second output compare register OCR1B, and starting from $00 up
again. When the counter value matches the contents of the Output Compare register
OCR1A, the PB1(OC1A) pin is set or cleared according to the settings of the
COM1A1/COM1A0 bits in the Timer/Counter1 Control Registers TCCR1. Refer to Table
12 for details.
Bit
$2F
Read/Write
Initial Value
Bit
$2E
Read/Write
Initial Value
CS13
1
1
1
1
1
1
1
1
MSB
MSB
R/W
R/W
CS12
7
0
7
0
0
0
0
0
1
1
1
1
R/W
R/W
6
0
6
0
CS11
0
0
1
1
0
0
1
1
R/W
R/W
5
0
5
0
CS10
R/W
R/W
4
0
4
0
0
1
0
1
0
1
0
1
R/W
R/W
3
0
3
0
Description
CK/8
CK/16
CK/32
CK/64
CK/128
CK/256
CK/512
CK/1024
R/W
R/W
2
0
2
0
R/W
R/W
1
0
1
0
ATtiny15L
LSB
R/W
LSB
R/W
0
0
0
0
OCR1A
TCNT1
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