75
8127B–AVR–08/09
ATtiny4/5/9/10
• Bits 1:0 – WGM01:0: Waveform Generation Mode
Combined with WGM03:2 bits of TCCR0B, these bits control the counting sequence of the coun-
ter, the source for maximum (TOP) counter value, and what type of waveform to generate. See
Table 11-5. Modes of operation supported by the Timer/Counter unit are: Normal mode (coun-
ter), Clear Timer on Compare match (CTC) mode, and three types of Pulse Width Modulation
(PWM) modes. (“Modes of Operation” on page 62).
11.11.2 TCCR0B – Timer/Counter0 Control Register B
• Bit 7 – ICNC0: Input Capture Noise Canceler
Setting this bit (to one) activates the Input Capture Noise Canceler. When the noise canceler is
activated, the input from the Input Capture pin (ICP0) is filtered. The filter function requires four
successive equal valued samples of the ICP0 pin for changing its output. The Input Capture is
therefore delayed by four oscillator cycles when the noise canceler is enabled.
• Bit 6 – ICES0: Input Capture Edge Select
This bit selects which edge on the Input Capture pin (ICP0) that is used to trigger a capture
event. When the ICES0 bit is written to zero, a falling (negative) edge is used as trigger, and
when the ICES0 bit is written to one, a rising (positive) edge will trigger the capture.
Table 11-5. Waveform Generation Modes
Mode
WGM0
3:0 Mode of Operation TOP
Update of
OCR0x at
TOV0 Flag
Set on
0 0000 Normal 0xFFFF Immediate MAX
1 0001 PWM, Phase Correct, 8-bit 0x00FF TOP BOTTOM
2 0010 PWM, Phase Correct, 9-bit 0x01FF TOP BOTTOM
3 0011 PWM, Phase Correct, 10-bit 0x03FF TOP BOTTOM
40100CTC (
Clear Timer on Compare) OCR0A Immediate MAX
5 0101 Fast PWM, 8-bit 0x00FF TOP TOP
6 0110 Fast PWM, 9-bit 0x01FF TOP TOP
7 0111 Fast PWM, 10-bit 0x03FF TOP TOP
8 1000 PWM, Phase & Freq. Correct ICR0 BOTTOM BOTTOM
9 1001 PWM, Phase & Freq. Correct OCR0A BOTTOM BOTTOM
10 1010 PWM, Phase Correct ICR0 TOP BOTTOM
11 1011 PWM, Phase Correct OCR0A TOP BOTTOM
12 1100 CTC (
Clear Timer on Compare) ICR0 Immediate MAX
13 1101 (Reserved) – – –
14 1110 Fast PWM ICR0 TOP TOP
15 1111 Fast PWM OCR0A TOP TOP
Bit 7654 3210
0x2D ICNC0 ICES0
– WGM03 WGM02 CS02 CS01 CS00 TCCR0B
Read/Write R/W R/W R R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
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