ATmega169P datasheet(147/393 Pages) ATMEL

номер детали	ATmega169P

подробное описание детали	8-bit Microcontroller with 16K Bytes In-System Programmable Flash

PDF	393 Pages

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производитель	ATMEL [ATMEL Corporation]

домашняя страница	http://www.atmel.com

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147

8018N–AVR–08/09

ATmega169P

clearing) the OC2A Register at compare match between OCR2A and TCNT2 when the counter

decrements. The PWM frequency for the output when using phase correct PWM can be calcu-

lated by the following equation:

The N variable represents the prescale factor (1, 8, 32, 64, 128, 256, or 1024).

The extreme values for the OCR2A Register represent special cases when generating a PWM

waveform output in the phase correct PWM mode. If the OCR2A 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.

At the very start of period 2 in Figure 17-7 OCn has a transition from high to low even though

there is no Compare Match. The point of this transition is to guarantee symmetry around BOT-

TOM. There are two cases that give a transition without Compare Match.

• OCR2A changes its value from MAX, like in Figure 17-7. When the OCR2A value is MAX the

OCn pin value is the same as the result of a down-counting compare match. To ensure

symmetry around BOTTOM the OCn value at MAX must correspond to the result of an up-

counting Compare Match.

• The timer starts counting from a value higher than the one in OCR2A, and for that reason

misses the Compare Match and hence the OCn change that would have happened on the way

up.

fOCnxPCPWM

clk_I/O

N 510

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ATmega169P датащи(PDF) 147 Page - ATMEL Corporation