PWM Review
Symmetric PWM Waveform
Symmetric PWM Waveform
Counter
Counter
Compare
Compare
Period
Period
T
T
PWM
PWM
T
T
PWM
PWM
/T
/T
CMP
CMP
Pin
Pin
(active high)
(active high)
Interrupts
Interrupts
Period
Compare
Counter
General Purpose Timer
T
PWM
/T
CMP
Pin
Compare
Compare
Compare
Full Compare Units
PWM1
PWM2
PWM3
PWM4
PWM5
PWM6
Each C28x event manager (EVA and EVB) is capable of generating five independent PWM
signals. Up to two different carrier frequencies can be independently selected as follows:
4 PWM @ freq1, 1 PWM @ freq2
Of course, frequency 1 need not differ from frequency 2.
In addition, three PWM signals may be generated which are compliments of three of the above
listed five (i.e. full compare units). This forms three complimentary pairs of PWM, and is
intended for use as input to a three-phase power converter.
Two different compare types exist on each C28x event managers (EVA and EVB) for generating
PWM signals:
1. General Purpose Timer Compares
2. Compare Units
Each uses one of the general purpose timers for clocking the PWM calculation, and these timers
will be covered next.
C28x - Event Manager 7 - 7
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