UM10413
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User manual
Rev. 1 — 16 December 2011
195 of 268
NXP Semiconductors
UM10413
MPT612 User manual
22.5.10 PWM Control register (PWMCON, TIMER3: PWM3CON - 0xE007 4074)
The PWM control register is used to configure the match outputs as PWM outputs. Each
match output can be independently set to perform either as PWM output or as match
output whose function is controlled by the external match register (EMR).
For each timer, a maximum of three single edge-controlled PWM outputs can be selected
on the MATn.2:0 outputs. One additional match register determines the PWM cycle
length. When a match occurs in any of the other match registers, the PWM output is set to
HIGH. The timer is reset by the match register that is configured to set the PWM cycle
length. When the timer is reset to zero, all currently HIGH match outputs configured as
PWM outputs are cleared.
22.5.11 Rules for single edge-controlled PWM outputs
•
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.
•
Each PWM output goes HIGH when its match value is reached. If no match occurs
(that is, the match value is greater than the PWM cycle length), the PWM output
remains continuously LOW.
•
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 is cleared on the next start of
the next PWM cycle.
Table 182. External match control
EMR[11:10], EMR[9:8],
EMR[7:6], or EMR[5:4]
Function
00
do nothing
01
clear the corresponding External Match bit/output to 0 (MATn.m pin is LOW if pinned out)
10
set the corresponding External Match bit/output to 1 (MATn.m pin is HIGH if pinned out)
11
toggle the corresponding External Match bit/output
Table 183: PWM Control register (PWMCON, TIMER3: PWM3CON - address 0xE007 4074) bit
description
Bit
Symbol
Description
Reset value
0
PWM enable
if logic 1, PWM mode is enabled for MATn.0. If logic 0,
MATn.0 is controlled by EM0.
0
1
PWM enable
if logic 1, PWM mode is enabled for MATn.1. If logic 0,
MATn.1 is controlled by EM1.
0
2
PWM enable
if logic 1, PWM mode is enabled for MATn.2. If logic 0,
MATn.2 is controlled by EM2.
0
3
PWM enable
if logic 1, PWM mode is enabled for MATn.3. If logic 0,
MATn.3 is controlled by EM3.
Remark:
It is recommended to use MATn.3 to set PWM
cycle.
0
4:32
-
reserved, user software must not write logic 1s to
reserved bits; value read from a reserved bit is not
defined
n/a