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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
432 of 571
NXP Semiconductors
UM10316
Chapter 25: LPC29xx Pulse Width Modulator (PWM)
illustrates the carrier signal (Timer1, 50% duty cycle) the internal PWM
signal and the modulated output signal of the PWM. The flowchart below shows how to
configure the PWM carrier input to achieve this result:
5.
PWM register overview
The PWM registers are shown in
. They have an offset to the base address
PWM RegBase which can be found in the memory map; see
Fig 113.Modulation of PWM and timer carrier
Fig 114. Carrrier-input configuration flowchart
t
Internal
PWM
PWM output
t
t
Timer1
output
MSCSS timer0
resolution = 1 µs
PWM in continuous
mode, sync_out
activated, sync_in
and shadow-register
update triggered
by SW
Configure PWM0 output 0,
disable trap, enable
carrier (burst mode)
Write first configuration
to PWM, duty cycle 50%
MSCSS timer0 match
after 10 µs , carrier
with 50 kHz
and 50% duty cycle
Configure MSCSS timer1,
enable match 0 output,
reset on match, toggle
output on match event
Table 345. PWM register overview (base address: 0xE00C 5000 (PWM0), 0xE00C 6000 (PWM1), 0xE00C 7000
(PWM2), 0xE00C 8000 (PWM3))
Address
Access Reset
Value
Name
Description
Reference
000h
R/W
0000 0000h MODECTL
Main control register
see
004h
R/W
0001 003Fh TRPCTL
Controls the behavior of PWM outputs
when there is an event on the PWMx
TRAP input pin
see
008h
R/W
0000 0000h CAPTCTL
Controls the behavior of the
Capture_Registers and associated pins
see
00Ch
R/W
0000 0000h CAPTSRC
Controls the source of the capture events
see
010h
R/W
0000 003Fh CTRL
Controls the PWM output behavior.
see