TBCTR
EPWMxA
EPWMxB
TBPRD
value
CA
CA
CA
CA
CBCB
CB
CB
CB
Action-Qualifier (AQ) Submodule
Figure 2-24. Up-Down-Count, Dual Edge Symmetric Waveform, With Independent Modulation on
EPWMxA and EPWMxB — Active Low
A PWM period = 2 x TBPRD × T
TBCLK
B Duty modulation for EPWMxA is set by CMPA, and is active low (that is, the low time duty is proportional to CMPA).
C Duty modulation for EPWMxB is set by CMPB and is active low (that is, the low time duty is proportional to CMPB).
D Outputs EPWMxA and EPWMxB can drive independent power switches
Example 2-5 contains a code sample showing initialization and run time for the waveforms in Figure 2-24 .
Use the code in Example 2-1 to define the headers.
Example 2-5. Code Sample for Figure 2-24
// Initialization Time
// = = = = = = = = = = = = = = = = = = = = = = = =
EPwm1Regs.TBPRD = 600; // Period = 2 × 600 TBCLK counts
EPwm1Regs.CMPA.half.CMPA = 400; // Compare A = 400 TBCLK counts
EPwm1Regs.CMPB = 500; // Compare B = 500 TBCLK counts
EPwm1Regs.TBPHS = 0; // Set Phase register to zero
EPwm1Regs.TBCNT = 0; // clear TB counter
EPwm1Regs.TBCTL.bit.CTRMODE = TB_UPDOWN; // Symmetric
xEPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE; // Phase loading disabled
xEPwm1Regs.TBCTL.bit.PRDLD = TB_SHADOW;
EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_DISABLE;
EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1; // TBCLK = SYSCLKOUT
EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV1;
EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;
EPwm1Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;
EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO; // load on CTR = Zero
EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO; // load on CTR = Zero
EPwm1Regs.AQCTLA.bit.CAU = AQ_SET;
EPwm1Regs.AQCTLA.bit.CAD = AQ_CLEAR;
EPwm1Regs.AQCTLB.bit.CBU = AQ_SET;
EPwm1Regs.AQCTLB.bit.CBD = AQ_CLEAR;
//
// Run Time
// = = = = = = = = = = = = = = = = = = = = = = = =
EPwm1Regs.CMPA.half.CMPA = Duty1A; // adjust duty for output EPWM1A
EPwm1Regs.CMPB = Duty1B; // adjust duty for output EPWM1B
SPRU791D – November 2004 – Revised October 2007 ePWM Submodules 47
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