UM10375 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
User manual Rev. 3 — 14 June 2011 277 of 368
NXP Semiconductors
UM10375
Chapter 15: LPC13xx 16-bit timer/counters (CT16B0/1)
15.8.13 Rules for single edge controlled PWM outputs
1. All single edge controlled PWM outputs go LOW at the beginning of each PWM cycle
(timer is set to zero) unless their match value is equal to zero.
2. Each PWM output will go HIGH when its match value is reached. If no match occurs
(i.e. the match value is greater than the PWM cycle length), the PWM output remains
continuously LOW.
3. If a match value larger than the PWM cycle length is written to the match register, and
the PWM signal is HIGH already, then the PWM signal will be cleared on the next start
of the next PWM cycle.
4. If a match register contains the same value as the timer reset value (the PWM cycle
length), then the PWM output will be reset to LOW on the next clock tick. Therefore,
the PWM output will always consist of a one clock tick wide positive pulse with a
period determined by the PWM cycle length (i.e. the timer reload value).
5. If a match register is set to zero, then the PWM output will go to HIGH the first time the
timer goes back to zero and will stay HIGH continuously.
Note: When the match outputs are selected to serve as PWM outputs, the timer reset
(MRnR) and timer stop (MRnS) bits in the Match Control Register MCR must be set to 0
except for the match register setting the PWM cycle length. For this register, set the
MRnR bit to 1 to enable the timer reset when the timer value matches the value of the
corresponding match register.
1 PWMEN1 PWM channel1 enable 0
0 CT16Bn_MAT1 is controlled by EM1.
1 PWM mode is enabled for CT16Bn_MAT1.
2 PWMEN2 PWM channel2 enable 0
0 Match channel 2 or pin CT16B0_MAT2 is controlled by
EM2. Match channel 2 is not pinned out on timer 1.
1 PWM mode is enabled for match channel 2 or pin
CT16B0_MAT2.
3 PWMEN3 PWM channel3 enable
Note: It is recommended to use to set the PWM cycle
because it is not pinned out.
0
0 Match channel 3 is controlled by EM3.
1 PWM mode is enabled for match channel 3.
31:4 - Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
NA
Table 267. PWM Control Register (TMR16B0PWMC - address 0x4000 C074 and
TMR16B1PWMC- address 0x4001 0074) bit description
Bit Symbol Value Description Reset
value
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