8-bit microcontroller with accelerated two-clock 80C51 core
Capture Noise Filter bit. If set, the capture logic needs to see four consecutive samples of
the same value in order to recognize an edge as a capture event. An event counter can be
set to delay a capture by a number of capture events.
8.19.6 PWM operation
PWM operation has two main modes, symmetrical and asymmetrical.
In asymmetrical PWM operation the CCU timer operates in down-counting mode
regardless of the direction control bit.
In symmetrical mode, the timer counts up/down alternately. The main difference from
basic timer operation is the operation of the compare module, which in PWM mode is
used for PWM waveform generation.
As with basic timer operation, when the PWM (compare) pins are connected to the
compare logic, their logic state remains unchanged. However, since bit FCO is used to
hold the halt value, only a compare event can change the state of the pin.
Fig 10. Asymmetrical PWM, down-counting mode
Fig 11. Symmetrical PWM
Product data sheet
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Rev. 8 — 12 January 2011
© NXP B.V. 2011. All rights reserved.
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