Datasheet
128
ATmega329/3290/649/6490
2552I–AVR–04/07
Note: 1. The CTC1 and PWM11:0 bit definition names are obsolete. Use the WGM12:0 definitions. However, the functionality and
location of these bits are compatible with previous versions of the timer.
TCCR1B – Timer/Counter1
Control Register B
• Bit 7 – ICNC1: Input Capture Noise Canceler
Setting this bit (to one) activates the Input Capture Noise Canceler. When the noise can-
celer is activated, the input from the Input Capture pin (ICP1) is filtered. The filter
function requires four successive equal valued samples of the ICP1 pin for changing its
output. The Input Capture is therefore delayed by four Oscillator cycles when the noise
canceler is enabled.
• Bit 6 – ICES1: Input Capture Edge Select
This bit selects which edge on the Input Capture pin (ICP1) that is used to trigger a cap-
ture event. When the ICES1 bit is written to zero, a falling (negative) edge is used as
trigger, and when the ICES1 bit is written to one, a rising (positive) edge will trigger the
capture.
When a capture is triggered according to the ICES1 setting, the counter value is copied
into the Input Capture Register (ICR1). The event will also set the Input Capture Flag
Table 64. Waveform Generation Mode Bit Description
(1)
Mode WGM13
WGM12
(CTC1)
WGM11
(PWM11)
WGM10
(PWM10)
Timer/Counter Mode of
Operation TOP
Update of
OCR1x at
TOV1 Flag
Set on
0 0 0 0 0 Normal 0xFFFF Immediate MAX
1 0 0 0 1 PWM, Phase Correct, 8-bit 0x00FF TOP BOTTOM
2 0 0 1 0 PWM, Phase Correct, 9-bit 0x01FF TOP BOTTOM
3 0 0 1 1 PWM, Phase Correct, 10-bit 0x03FF TOP BOTTOM
4 0 1 0 0 CTC OCR1A Immediate MAX
5 0 1 0 1 Fast PWM, 8-bit 0x00FF BOTTOM TOP
6 0 1 1 0 Fast PWM, 9-bit 0x01FF BOTTOM TOP
7 0 1 1 1 Fast PWM, 10-bit 0x03FF BOTTOM TOP
8 1 0 0 0 PWM, Phase and Frequency
Correct
ICR1 BOTTOM BOTTOM
9 1 0 0 1 PWM, Phase and Frequency
Correct
OCR1A BOTTOM BOTTOM
10 1 0 1 0 PWM, Phase Correct ICR1 TOP BOTTOM
11 1 0 1 1 PWM, Phase Correct OCR1A TOP BOTTOM
12 1 1 0 0 CTC ICR1 Immediate MAX
13 1 1 0 1 (Reserved) – – –
14 1 1 1 0 Fast PWM ICR1 BOTTOM TOP
15 1 1 1 1 Fast PWM OCR1A BOTTOM TOP
Bit 7654 3210
(0x81) ICNC1 ICES1 – WGM13 WGM12 CS12 CS11 CS10 TCCR1B
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