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UP
DOWN
UP
DOWN
2
0
3
4
1
2
3
1
2
0
3
4
1
2
0
3
1
TBCTR
TBCTR Direction
EPWMxA/EPWMxB
Case 2:
CMPA = 3, 25% Duty
Case 3:
CMPA = 2, 50% Duty
Case 3:
CMPA = 1, 75% Duty
Case 4:
CMPA = 0, 100% Duty
Case 1:
CMPA = 4, 0% Duty
EPWMxA/EPWMxB
EPWMxA/EPWMxB
EPWMxA/EPWMxB
EPWMxA/EPWMxB
Mode: Up-Down Count
TBPRD = 4
CAU = SET, CAD = CLEAR
0% - 100% Duty
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ePWM Submodules
Figure 23. Up-Down-Count Mode Symmetrical Waveform
The PWM waveforms in
through
show some common action-qualifier configurations.
The C-code samples in
through
shows how to configure an ePWM module for each
case. Some conventions used in the figures and examples are as follows:
•
TBPRD, CMPA, and CMPB refer to the value written in their respective registers. The active register,
not the shadow register, is used by the hardware.
•
CMPx, refers to either CMPA or CMPB.
•
EPWMxA and EPWMxB refer to the output signals from ePWMx
•
Up-Down means Count-up-and-down mode, Up means up-count mode and Dwn means down-count
mode
•
Sym = Symmetric, Asym = Asymmetric
43
SPRUG04A – October 2008 – Revised July 2009
TMS320x2833x, 2823x Enhanced Pulse Width Modulator (ePWM) Module
© 2008–2009, Texas Instruments Incorporated