Hi.
I'm using tgeTMS320F28035PNT which comes with the isolated control card (CC2803X ISO DIMM Rev 1.3.
Tool is Code Composer Studio 6.1.1.00022
I am configuring the PWM to be forced low when comparator 3 goes high. Everything seems to work fine, except the outputs take many microseconds to go to 0. At first I thought I was configuring the system to go to high impedance, but that doesn't seem to be the case. Here's my code:
EALLOW; Comp3Regs.COMPCTL.bit.COMPDACEN =0x1; // Enable comparator block Comp3Regs.COMPCTL.bit.QUALSEL =0x0; // 1 clock cycle before triggering event Comp3Regs.COMPCTL.bit.SYNCSEL =0x0; // asynchronous version of the COMP signal is passed to the EPWM/GPIO module Comp3Regs.COMPCTL.bit.CMPINV =0x0; // Output of the comparator is passed directly Comp3Regs.COMPCTL.bit.COMPSOURCE =0x0; // inverting input of the comparator is connected to the internal DAC Comp3Regs.DACVAL.bit.DACVAL =512; // set DAC input to peak trip point AdcRegs.COMPHYSTCTL.bit.COMP3_HYST_DISABLE = 0x1; //hysteresis disabled // One shot latching protection EPwm1Regs.DCTRIPSEL.bit.DCAHCOMPSEL = DC_COMP3OUT; //Compare high linked to comparator 3 EPwm1Regs.TZDCSEL.bit.DCAEVT1 = TZ_DCAH_HI; //0x2 EPwm1Regs.DCACTL.bit.EVT1SRCSEL = DC_EVT1; //0x0 EPwm1Regs.DCACTL.bit.EVT1FRCSYNCSEL = DC_EVT_ASYNC;//0x1 EPwm2Regs.DCTRIPSEL.bit.DCAHCOMPSEL = DC_COMP3OUT; //Compare high linked to comparator 3 EPwm2Regs.TZDCSEL.bit.DCAEVT1 = TZ_DCAH_HI; //0x2 EPwm2Regs.DCACTL.bit.EVT1SRCSEL = DC_EVT1; //0x0 EPwm2Regs.DCACTL.bit.EVT1FRCSYNCSEL = DC_EVT_ASYNC; //0x1 EPwm1Regs.TZSEL.bit.DCAEVT1 = 0x1; //One shot enable of trip zone for epwm1 EPwm2Regs.TZSEL.bit.DCAEVT1 = 0x1; //One shot enable of trip zone for epwm2 // What do we want the OST/CBC events to do? EPwm1Regs.TZCTL.bit.DCAEVT1 = TZ_FORCE_LO; // 0x2 EPWMxA will go low EPwm2Regs.TZCTL.bit.DCAEVT1 = TZ_FORCE_LO; // 0x2 EPWMxB will go low EDIS; //clear any spurious trips EPwm1Regs.TZCLR.bit.OST=1; EPwm1Regs.TZCLR.bit.DCAEVT1=1; EPwm2Regs.TZCLR.bit.OST=1; EPwm2Regs.TZCLR.bit.DCAEVT1=1;
With this configuration the outputs look like this:
Yellow trace is the comparator input, and the remaining traces are two of my pwm outputs (the blue is not switching at that point, but that's ok). It looks like the outputs are going into high impedance instead of being forced low. Any suggestions on how to fix this so that the output goes "instantly" to 0?
Thanks in advance.
