TMS320F28379S: Relationship between PWM syncing with no phase and interrupt triggering

Yiu Hang Li

Part Number: TMS320F28379S

Hi there,

I got a question regarding the PWM syncing and interrupt.

We are syncing PWM with an external signal with no phase (TBPHS = 0). We also set PWM interrupt will be triggered when counter = 0 or TBPRD (ETSEL[INTSEL] = ET_CTR_PRDZERO). The program seems to work fine, the motor did run.

But thinking a bit further we come up with a scenario that should have caused problem: Let say TBCTR just reach 0 and a PWM ISR is triggered. But shortly after, when TBCTR is at let say 4, external signal comes in, with the syncing mechanism TBCTR will be reset to 0. In this case will this cause interrupt signal to be fired again? If so is that mean an extra ISR will be running right after current ISR?

I tried to illustrate the scenario in the following figure:

Thanks for reading, any reply is appreciated

over 6 years ago

0 Nima Eskandari over 6 years ago

TI__Guru 52040 points

Yes every time the TBCTR becomes 0, an interrupt will fire. You can set TBPHS=1 so it wont change TBCTR to 0.

Nima

0 Yiu Hang Li over 6 years ago in reply to Nima Eskandari

Intellectual 460 points

Thanks for the reply Nima, your anwser clear our doubt.

Just one more question though, is there any good way to monitor ISR? We have tried toggling IO when enter and leave ISR, it works but is clumsy. It's difficult to hold oscilloscope probe steady and the number of ISRs we can monitored are limited by the number of spare IO on the board.

0 Nima Eskandari over 5 years ago in reply to Yiu Hang Li

TI__Guru 52040 points

Maybe a good way is having a variable that increments every interrupt. Then transfer that variable up to a PC for debugging through SCI and COM ports.

0 Yiu Hang Li over 5 years ago in reply to Nima Eskandari

Intellectual 460 points

Thanks Nima!

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28379S: Relationship between PWM syncing with no phase and interrupt triggering