ATMEGA128-16AU SL383 Atmel, ATMEGA128-16AU SL383 Datasheet - Page 131

• Manufacturer Part Number: ATMEGA128-16AU SL383
• Manufacturer: Atmel

Timer/Counter
Timing Diagrams
2467S–AVR–07/09
The extreme values for the OCRnx Register represent special cases when generating a PWM
waveform output in the phase correct PWM mode. If the OCRnx is set equal to BOTTOM the
output will be continuously low and if set equal to TOP the output will be set to high for non-
inverted PWM mode. For inverted PWM the output will have the opposite logic values.
If OCRnA is used to define the TOP value (WGMn3:0 = 9) and COMnA1:0 = 1, the OCnA Output
will toggle with a 50% duty cycle.
The Timer/Counter is a synchronous design and the timer clock (clk
clock enable signal in the following figures. The figures include information on when interrupt
flags are set, and when the OCRnx Register is updated with the OCRnx buffer value (only for
modes utilizing double buffering).
Figure 55. Timer/Counter Timing Diagram, Setting of OCFnx, no Prescaling
Figure 56
Figure 56. Timer/Counter Timing Diagram, Setting of OCFnx, with Prescaler (f
TCNTn
OCRnx
TCNTn
OCRnx
OCFnx
OCFnx
(clk
(clk
clk
clk
clk
clk
I/O
I/O
I/O
I/O
Tn
Tn
/1)
shows the same timing data, but with the prescaler enabled.
/8)
OCRnx - 1
OCRnx - 1
Figure 55
OCRnx
OCRnx
shows a timing diagram for the setting of OCFnx.
OCRnx Value
OCRnx Value
OCRnx + 1
OCRnx + 1
Tn
) is therefore shown as a
ATmega128
OCRnx + 2
OCRnx + 2
clk_I/O
/8)
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