Philips Semiconductors
P89LPC932A1
8-bit microcontroller with accelerated two-clock 80C51 core
7.19.6 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.
TOR2
compare value
timer value
0x0000
non-inverted
inverted
Fig 8. Asymmetrical PWM, down-counting.
002aaa893
TOR2
compare value
timer value
0
non-inverted
inverted
Fig 9. Symmetrical PWM.
002aaa894
9397 750 14871
Product data sheet
Rev. 02 — 10 May 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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