P89LPC938 NXP Semiconductors, P89LPC938 Datasheet - Page 30

• Manufacturer Part Number: P89LPC938
• Description: The P89LPC938 is a single-chip microcontroller, available in low cost packages, based ona high performance processor architecture that executes instructions in two to four clocks,six times the rate of standard 80C51 devices
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 14051
Product data sheet
7.19.6 PWM operation
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.
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 8. Asymmetrical PWM, down-counting.
Fig 9. Symmetrical PWM.
compare value
compare value
non-inverted
non-inverted
timer value
timer value
inverted
0x0000
inverted
TOR2
TOR2
Rev. 01 — 25 February 2005
0
8-bit microcontroller with 10-bit A/D converter
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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