AT90USB646_14 Datasheet, PDF (108/456 Pages) ATMEL Corporation – USB boot loader programmed by default in the factory

Figure 14-9. Timer/Counter timing diagram, with prescaler (f_{clk_I/O}/8).
clk_I/O
clk_Tn
(clk_I/O/8)
TCNTn
MAX - 1
MAX
BOTTOM
TOVn
BOTTOM + 1
Figure 14-10 shows the setting of OCF0B in all modes and OCF0A in all modes except CTC
mode and PWM mode, where OCR0A is TOP.
Figure 14-10. Timer/Counter timing diagram, setting of OCF0x, with prescaler (f_{clk_I/O}/8).
clk_I/O
clk_Tn
(clk_I/O/8)
TCNTn
OCRnx - 1
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx
OCRnx Value
OCFnx
Figure 14-11 shows the setting of OCF0A and the clearing of TCNT0 in CTC mode and fast
PWM mode where OCR0A is TOP.
Figure 14-11. Timer/Counter timing diagram, clear timer on Compare Match mode, with pres-
caler (f_{clk_I/O}/8)
clk_I/O
clk_Tn
(clkI/O /8)
TCNTn
(CTC)
OCRnx
OCFnx
TOP - 1
TOP
TOP
BOTTOM
BOTTOM + 1
14.8 8-bit Timer/Counter register description
14.8.1
TCCR0A – Timer/Counter Control Register A
Bit
Read/write
Initial value
7
6
5
4
3
COM0A1 COM0A0 COM0B1 COM0B0 –
R/W
R/W
R/W
R/W
R
0
0
0
0
0
108 AT90USB64/128
2
1
0
–
WGM01 WGM00 TCCR0A
R
R/W
R/W
0
0
0
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