CCS/LAUNCHXL-F28379D: Problem to select EPWM

void ConfigureEPWM(void)
{
    EALLOW;
                                                           // Assumes ePWM clock is already enabled
    EPwm2Regs.ETSEL.bit.SOCAEN    = 1;                     // Enable SOC on A group
    EPwm2Regs.ETSEL.bit.SOCASEL   = 3;                     // Select SOC on up-count
    EPwm2Regs.ETPS.bit.SOCAPRD = 1;                        // Generate pulse on 1st event
    EPwm2Regs.TBPRD = 19;                                  // Set period to 2.5 MHz
    EPwm2Regs.TBCTL.bit.CTRMODE = 0 ;                      // freeze counter
    EDIS;
}

AdcaRegs.ADCSOC0CTL.bit.TRIGSEL = 7;  

It is workin fine. However, when I use 

{
    EALLOW;
                                                           // Assumes ePWM clock is already enabled
    EPwm3Regs.ETSEL.bit.SOCAEN    = 1;                     // Enable SOC on A group
    EPwm3Regs.ETSEL.bit.SOCASEL   = 3;                     // Select SOC on up-count
    EPwm3Regs.ETPS.bit.SOCAPRD = 1;                        // Generate pulse on 1st event
    EPwm3Regs.TBPRD = 19;                                  // Set period to 2.5 MHz
    EPwm3Regs.TBCTL.bit.CTRMODE = 0 ;                      // freeze counter
    EDIS;
}

AdcaRegs.ADCSOC0CTL.bit.TRIGSEL = 8;