ATTINY15 ATMEL [ATMEL Corporation], ATTINY15 Datasheet - Page 33

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

Timer/Counter1 Output
Compare RegisterB – OCR1B
1187D–12/01
The Output Compare Register1 (OCR1B) is an 8-bit read/write register. This register is
used in the PWM mode only, and it limits the top value to which the Timer/Counter1
keeps counting. After reaching OCR1B in PWM mode, the counter starts from $00.
Table 13. PWM Outputs when OCR1A = $00 or OCR1B
In PWM mode, the Timer Overflow Flag (TOV1) is set as in normal Timer/Counter
mode. Timer Overflow Interrupt1 operates exactly as in normal Timer/Counter mode,
i.e., it is executed when TOV1 is set provided that Timer Overflow Interrupt and global
interrupts are enabled. This also applies to the Timer Output Compare A flag and
interrupt.
The frequency of the PWM will be Timer Clock Frequency divided by OCR1B value + 1.
Table 14. Timer/Counter1 Clock Prescale Select
Bit
$2D
Read/Write
Initial Value
COM1A1
Clock Selection
1
1
1
1
PCK/8
PCK/4
PCK/4
PCK/2
PCK/2
PCK/2
PCK/2
PCK/2
MSB
R/W
PCK
PCK
PCK
PCK
PCK
PCK
CK
7
1
R/W
6
1
COM1A0
0
0
1
1
R/W
5
1
R/W
OCR1B
4
1
159
159
213
159
255
213
181
159
141
255
231
213
195
181
169
OCR1B
OCR1B
OCR1B
R/W
$00
$00
3
1
R/W
2
1
PWM Frequency
R/W
1
1
Output PWMn
100 kHz
110 kHz
120 kHz
130 kHz
140 kHz
150 kHz
10 kHz
20 kHz
30 kHz
40 kHz
50 kHz
60 kHz
70 kHz
80 kHz
90 kHz
ATtiny15L
LSB
R/W
0
1
H
H
L
L
OCR1B
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