ATtiny15L
Timer/Counter1 Output Compare RegisterB – OCR1B
Bit |
|
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
|
$2D |
MSB |
|
|
|
|
|
|
LSB |
OCR1B |
|
|
|
|
|
|
|
|
|
|
|
|
Read/Write |
R/W |
R/W |
R/W |
R/W |
R/W |
R/W |
R/W |
R/W |
|
|
Initial value |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
|
|
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
COM1A1 |
COM1A0 |
OCR1B |
Output PWMn |
|
|
|
|
1 |
0 |
$00 |
L |
|
|
|
|
1 |
0 |
OCR1B |
H |
|
|
|
|
1 |
1 |
$00 |
H |
|
|
|
|
1 |
1 |
OCR1B |
L |
|
|
|
|
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
Clock Selection |
OCR1B |
PWM Frequency |
|
|
|
CK |
159 |
10 kHz |
|
|
|
PCK/8 |
159 |
20 kHz |
|
|
|
PCK/4 |
213 |
30 kHz |
|
|
|
PCK/4 |
159 |
40 kHz |
|
|
|
PCK/2 |
255 |
50 kHz |
|
|
|
PCK/2 |
213 |
60 kHz |
|
|
|
PCK/2 |
181 |
70 kHz |
|
|
|
PCK/2 |
159 |
80 kHz |
|
|
|
PCK/2 |
141 |
90 kHz |
|
|
|
PCK |
255 |
100 kHz |
|
|
|
PCK |
231 |
110 kHz |
|
|
|
PCK |
213 |
120 kHz |
|
|
|
PCK |
195 |
130 kHz |
|
|
|
PCK |
181 |
140 kHz |
|
|
|
PCK |
169 |
150 kHz |
|
|
|
31