Rainbow-electronics ATmega128L Uživatelský manuál stáhnout pdf (Strana 149)

149

ATmega128(L)

2467B–09/01

The N variable represents the prescale factor (1, 8, 64, 256, or 1024).

The extreme values for the OCR2 register represent special cases when generating a

PWM waveform output in the phase correct PWM mode. If the OCR2 is set equal to

BOTTOM, the output will be continuously low and if set equal to MAX the output will be

continuously high for non-inverted PWM mode. For inverted PWM the output will have

the opposite logic values.

Timer/Counter Timing

Diagrams

The Timer/Counter is a synchronous design and the timer clock (clk

) is therefore

shown as a clock enable signal in the following figures. The figures include information

on when interrupt flags are set.

Figure 67 contains timing data for basic Timer/Counter

operation. The figure shows the count sequence close to the MAX value in all modes

other than phase correct PWM mode.

Figure 67. Timer/Counter Timing Diagram, no Prescaling

Figure 68 shows the same timing data, but with the prescaler enabled.

Figure 68. Timer/Counter Timing Diagram, with Prescaler (f

clk_I/O

/8)

Figure 69 shows the setting of OCF2 in all modes except CTC mode.

clk

(clk

I/O

/1)

TOVn

clk

I/O

TCNTn

MAX - 1 MAX BOTTOM BOTTOM + 1

TOVn

TCNTn

MAX - 1 MAX BOTTOM BOTTOM + 1

clk

I/O

clk

(clk

I/O

/8)

1 2 ... 144 145 146 147 148 149 150 151 152 153 154 ... 330 331

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Rainbow-electronics ATmega128L Uživatelský manuál Strana 149