DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
RAFT DRAFT DRAFT DRAFT DRAFT D
DRAFT
D
RAFT DRA
FT DRAFT DRAFT DRAFT DRA
UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
439 of 571
NXP Semiconductors
UM10316
Chapter 25: LPC29xx Pulse Width Modulator (PWM)
[1]
There are only three external capture inputs per PWM. PWMx CAPT2 is also connected to CAPT3.
5.6 PWM control register
The CTRL register selects the active level for each output. It also allows mixing of the
external carrier signal with the internal PWM generated signals.
shows the bit assignment of the CTRL register.
[1]
Changing the ACT_LVL bits may cause the outputs to change directly if the PWM outputs are enabled
through the SCU.
5.7 PWM period register
The PRD register contains the cycle period value minus 1. PWM output period is:
(PRD + 1)
×
(PRSC + 1) system clock cycles
Given the desired PWM period, values for PRD and PRSC can be derived from:
PRD
×
PRSC = t
PWM
/ t
clk(sys)
−
1
1 and 0
CAPT_SRC0[1:0]
R/W
Select the source of capture channel 0 to
trigger capture of the PWM
00*
PWMx CAPT0 signal, x is index of PWM
01
Sync_in signal
10
PWMx TRAP signal, x is index of PWM
11
Trans_enable_in signal
Table 350. CAPSRC register bit description
…continued
* = reset value
Bit
Symbol
Access
Value
Description
Table 351. CTRL register bit description
* = reset value
Bit
Symbol
Access
Value
Description
31 to 22 reserved
R
-
Reserved; do not modify. Read as logic 0
21
BURST_ENA[5]
R/W
1
PWM 5 is mixed with the external carrier input
0*
:
:
:
:
:
16
BURST_ENA[0]
R/W
1
PWM 0 is mixed with the external carrier input
0*
15 to 6
reserved
R
-
Reserved; do not modify. Read as logic 0
5
ACT_LVL[5]
R/W
1*
PWM 5 output is at a HIGH level for the active
state.
0
PWM 5 output is at a LOW level for the active
state.
:
:
:
:
:
0
ACT_LVL[0]
R/W
1*
PWM 0 output is at a HIGH level for the active
state.
0
PWM 0 output is at a LOW level for the active
state.