Resolution shows how many bit is required to express the value in the OCR1C register. It is calculated by following equation

ResolutionPWM = log2(OCR1C + 1).

Table 14-6. Timer/Counter1 Clock Prescale Select in the Asynchronous Mode

PWM Frequency	Clock Selection	CS13..CS10	OCR1C	RESOLUTION
20 kHz	PCK/16	0101	199	7.6
30 kHz	PCK/16	0101	132	7.1
40 kHz	PCK/8	0100	199	7.6
50 kHz	PCK/8	0100	159	7.3
60 kHz	PCK/8	0100	132	7.1
70 kHz	PCK/4	0011	228	7.8
80 kHz	PCK/4	0011	199	7.6
90 kHz	PCK/4	0011	177	7.5
100 kHz	PCK/4	0011	159	7.3
110 kHz	PCK/4	0011	144	7.2
120 kHz	PCK/4	0011	132	7.1
130 kHz	PCK/2	0010	245	7.9
140 kHz	PCK/2	0010	228	7.8
150 kHz	PCK/2	0010	212	7.7
160 kHz	PCK/2	0010	199	7.6
170 kHz	PCK/2	0010	187	7.6
180 kHz	PCK/2	0010	177	7.5
190 kHz	PCK/2	0010	167	7.4
200 kHz	PCK/2	0010	159	7.3
250 kHz	PCK	0001	255	8.0
300 kHz	PCK	0001	212	7.7
350 kHz	PCK	0001	182	7.5
400 kHz	PCK	0001	159	7.3
450 kHz	PCK	0001	141	7.1
500 kHz	PCK	0001	127	7.0

15. 8-bit Timer/Counter1 in ATtiny15 Mode

The ATtiny15 compatibility mode is selected by writing the code “0011” to the CKSEL fuses (if any other code is written, the Timer/Counter1 is working in normal mode). When selected the ATtiny15 compatibility mode provides an ATtiny15 backward compatible prescaler and Timer/Counter. Furthermore, the clocking system has same clock frequencies as in ATtiny15.

90 ATtiny25/45/85 Auto

7598C–AVR–09/06