Chapter 25 FlexPWM
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
681
25.7
Functional description
25.7.1
Center-aligned PWMs
Each submodule has its own timer that is capable of generating PWM signals on two output pins. The
edges of each of these signals are controlled independently as shown in
.
Figure 25-29. Center-aligned example
The submodule timers only count in the up direction and then reset to the INIT value. Instead of having a
single value that determines pulse width, there are two values that must be specified: the turn on edge and
the turn off edge. This double action edge generation not only gives the user control over the pulse width,
but over the relative alignment of the signal as well. As a result, there is no need to support separate PWM
alignment modes since the PWM alignment mode is inherently a function of the turn on and turn off edge
values.
also illustrates an additional enhancement to the PWM generation process. When the counter
resets, it is reloaded with a user-specified value, which may or may not be zero. If the value chosen happens
to be the 2’s complement of the modulus value, then the PWM generator operates in “signed” mode. This
means that if each PWM’s turn on and turn off edge values are also the same number but only different in
their sign, the “on” portion of the output signal will be centered around a count value of zero. Therefore,
only one PWM value needs to be calculated in software and then this value and its negative are provided
to the submodule as the turn off and turn on edges respectively. This technique will result in a pulse width
that always consists of an odd number of timer counts. If all PWM signal edge calculations follow this
same convention, then the signals will be center-aligned with respect to each other, which is the goal. Of
VAL1 (0x0100)
VAL3
VAL5
VAL0 (0x0000)
VAL4
VAL2
INIT (0xFF00)
PWMA
PWMB
Содержание SAFE ASSURE Qorivva MPC5601P
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Страница 578: ...Chapter 22 FlexCAN MPC5602P Microcontroller Reference Manual Rev 4 578 Freescale Semiconductor ...
Страница 708: ...Chapter 25 FlexPWM MPC5602P Microcontroller Reference Manual Rev 4 708 Freescale Semiconductor ...
Страница 742: ...Chapter 26 eTimer MPC5602P Microcontroller Reference Manual Rev 4 742 Freescale Semiconductor ...
Страница 760: ...Chapter 27 Functional Safety MPC5602P Microcontroller Reference Manual Rev 4 760 Freescale Semiconductor ...
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