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TBCTR

EPWMxA

EPWMxB

TBPRD

value

CAZ P CB Z P CB CA Z P

Z P CA Z P CA Z PCBCB

Action-Qualifier (AQ) Submodule

www.ti.com

Figure 2-21. Up, Single Edge Asymmetric Waveform, With Independent Modulation on EPWMxA and

EPWMxB—Active High

A PWM period = (TBPRD + 1 ) × T

TBCLK

B Duty modulation for EPWMxA is set by CMPA, and is active high (that is, high time duty proportional to CMPA).

C Duty modulation for EPWMxB is set by CMPB and is active high (that is, high time duty proportional to CMPB).

D The "Do Nothing" actions ( X ) are shown for completeness, but will not be shown on subsequent diagrams.

E Actions at zero and period, although appearing to occur concurrently, are actually separated by one TBCLK period.

TBCTR wraps from period to 0000.

Example 2-2 contains a code sample showing initialization and run time for the waveforms in Figure 2-21 .

Example 2-2. Code Sample for Figure 2-21

// Initialization Time

// = = = = = = = = = = = = = = = = = = = = = = = =

EPwm1Regs.TBPRD = 600; // Period = 601 TBCLK counts

EPwm1Regs.CMPA.half.CMPA = 350; // Compare A = 350 TBCLK counts

EPwm1Regs.CMPB = 200; // Compare B = 200 TBCLK counts

EPwm1Regs.TBPHS = 0; // Set Phase register to zero

EPwm1Regs.TBCTR = 0; // clear TB counter

EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;

EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE; // Phase loading disabled

EPwm1Regs.TBCTL.bit.PRDLD = TB_SHADOW;

EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_DISABLE;

EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1; // TBCLK = SYSCLK

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.ZRO = AQ_SET;

EPwm1Regs.AQCTLA.bit.CAU = AQ_CLEAR;

EPwm1Regs.AQCTLB.bit.ZRO = AQ_SET;

EPwm1Regs.AQCTLB.bit.CBU = AQ_CLEAR;

// Run Time

// = = = = = = = = = = = = = = = = = = = = = = = =

EPwm1Regs.CMPA.half.CMPA = Duty1A; // adjust duty for output EPWM1A

EPwm1Regs.CMPB = Duty1B; // adjust duty for output EPWM1B

44 ePWM Submodules SPRU791F – November 2004 – Revised July 2009

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