Rainbow Electronics ATmega3290P_V - Manual (Page 125)

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ATmega329/3290/649/6490
2552H–AVR–11/06
Figure 51. Timer/Counter Timing Diagram, Setting of OCF1x, with Prescaler (f
clk_I/O
/8)
Figure 52 shows the count sequence close to TOP in various modes. When using phase
and frequency correct PWM mode the OCR1x Register is updated at BOTTOM. The
timing diagrams will be the same, but TOP should be replaced by BOTTOM, TOP-1 by
BOTTOM+1 and so on. The same renaming applies for modes that set the TOV1 Flag
at BOTTOM.
Figure 52. Timer/Counter Timing Diagram, no Prescaling
Figure 53 shows the same timing data, but with the prescaler enabled.
OCFnx
OCRnx
TCNTn
OCRnx Value
OCRnx - 1 OCRnx OCRnx + 1 OCRnx + 2
clk
I/O
clk
Tn
(clk
I/O
/8)
TOVn (FPWM)
and ICFn (if used
as TOP)
OCRnx
(Update at TOP)
TCNTn
(CTC and FPWM)
TCNTn
(PC and PFC PWM)
TOP - 1 TOP TOP - 1 TOP - 2
Old OCRnx Value New OCRnx Value
TOP - 1 TOP BOTTOM BOTTOM + 1
clk
Tn
(clk
I/O
/1)
clk
I/O