TMS320F28035: question about CMPA load

Huihuang Chen

Expert 4060 points

Part Number: TMS320F28035

Hi Champ,

I found a problem when using ePWM module.

below is the detail:

The ePWM2 CMPA be load on the TBCTR=TBPRD event.

The ePWM2 will generate the interrupt on the TBCTR = TBPRD event.

At the watch window we found the CMPAM always not update. but the CMPA value be write successful.

But the ePWM2 ISR can always execute normally.

So may i know in any case the TBCTR = TBPRD event happened but the CMPA cannot loading on the TBCTR=TBPRD event.?

over 7 years ago

0 Vasudha Bhadoria over 7 years ago

TI__Genius 10845 points

Hi,

I am looking into this & will get back to you.

Thanks
Vasudha

0 Vasudha Bhadoria over 7 years ago in reply to Vasudha Bhadoria

TI__Genius 10845 points

Hi Chen,

I assume the shadow mode is on and load is configured to happen on TBCTR=TBPTR. Are you relying on the watch window to conclude that CMPA is not getting updated? Read the CMPA value in code to check whether the correct value is getting written in the CMPA. You can check in the ISR to confirm.

Thanks
Vasudha

0 Huihuang Chen over 7 years ago in reply to Vasudha Bhadoria

TI__Expert 4060 points

Hi Vasudha,

Yes, the shadow mode is on and load is configured to happen on TBCTR=TBPRD.

Of course , we also verify it from the real PWM output. the real output PWM duty also incorrect.

0 Vasudha Bhadoria over 7 years ago in reply to Huihuang Chen

TI__Genius 10845 points

Hi Chen,

Are you using global reload feature? Can you check if one shot mode is active? This could be one reason for the load not happening.

Thanks
Vasudha

0 Huihuang Chen over 7 years ago in reply to Vasudha Bhadoria

TI__Expert 4060 points

Hi Vasudha,

F28035 don't support global reload feature.

0 Vasudha Bhadoria over 7 years ago in reply to Huihuang Chen

TI__Genius 10845 points

Hi Chen,

Were you able to root cause it? I looked into the registers for this device. I see there is a CMPCTL[SHDWAFULL] bit to determine if the shadow register is full. I guess this should be checked before writing to CMPA registers. Is it possible that the shadow register is getting overwritten before the load to active register? Let me know if you were able to resolve it.

Thanks
Vasudha

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TMS320F28035: question about CMPA load