TBCTR
EPWMxA
EPWMxB
TBPRD
value
Z
T
Z
T
Z
T
Action-Qualifier (AQ) Submodule
Example 2-3. Code Sample for Figure 2-22
// 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_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 = 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 TBCTR = Zero
EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO; // load on TBCTR = Zero
EPwm1Regs.AQCTLA.bit.PRD = AQ_CLEAR;
EPwm1Regs.AQCTLA.bit.CAU = AQ_SET;
EPwm1Regs.AQCTLB.bit.PRD = AQ_CLEAR;
EPwm1Regs.AQCTLB.bit.CBU = AQ_SET;
//
// Run Time
// = = = = = = = = = = = = = = = = = = = = = = = =
EPwm1Regs.CMPA.half.CMPA = Duty1A; // adjust duty for output EPWM1A
EPwm1Regs.CMPB = Duty1B; // adjust duty for output EPWM1B
Figure 2-23. Up-Count, Pulse Placement Asymmetric Waveform With Independent Modulation on
EPWMxA
A PWM frequency = 1/( (TBPRD + 1 ) × T
TBCLK
)
B Pulse can be placed anywhere within the PWM cycle (0000 - TBPRD)
C High time duty proportional to (CMPB - CMPA)
D EPWMxB can be used to generate a 50% duty square wave with frequency = 1/2 × ( (TBPRD + 1 ) × TBCLK )
Example 2-4 contains a code sample showing initialization and run time for the waveforms Figure 2-23 .
Use the code in Example 2-1 to define the headers.
SPRU791D – November 2004 – Revised October 2007 ePWM Submodules 45
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