TMS320F28075: If external clock stop, How to instantly stop PWM

Genius 3186 points

Part Number: TMS320F28075

May I have a question about F28075 clocking.

My customer want to do If external clock stop, instantly stop PWM.

First,

We tried NMI Missing Clock Detection Logic.

However this logic must need max 2^13 INTOSC1 clocks between after SYSCLK stoped timing and PWM trip event.
Second,

We tried Watchdog timer reset,

But this need max 512 * 2^8 INTOSC clocks like same as MCD logic.

Is there any way to if X1-X2 clock stopped, instantly stop PWM (generate PWM trip event)?

Thanks,

over 2 years ago

+1 Allison Nguyen over 2 years ago

TI__Mastermind 26400 points

Hi GR,

Can you further describe your setup? How are you measuring the timing of the delay between the stopped SYSCLK and the PWM trip? Also, what is causing the stopping of SYSCLK in your testing? Are you using TZ5 to generate the EPWM trip?

Regards,

Allison

0 GR over 2 years ago in reply to Allison Nguyen

Genius 3186 points

Hi Allison,

Allison Nguyen said:
Can you further describe your setup?

My customer is using external clock (use X1 X2 pin) for PLL source.

we want to do if X1-X2 short (crystal broken), instantly stop PWM.

Allison Nguyen said:
How are you measuring the timing of the delay between the stopped SYSCLK and the PWM trip?

the PRM trip timing must be delay to clock error by MCD logic counter.

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1177523/tms320f280049-missing-clock-detection-question-about-time-for-mcdscnt-to-overflow/4433342

Allison Nguyen said:
Are you using TZ5 to generate the EPWM trip?

I think PWM trip is genereted by MCD logic.

TMS320F2807x Microcontrollers Technical Reference Manua (Rev. F)

3.6.2 Missing Clock Detection Logic

Allison Nguyen said:
Also, what is causing the stopping of SYSCLK in your testing?

This test is if crystal broken, and X1-X2 short test.

Best regards,

+1 Allison Nguyen over 2 years ago in reply to GR

TI__Mastermind 26400 points

Hi GR,

What is the end application here? (Is there a reason the NMI with 819.2 us is unable to be used?). The only EPWM path directly from a clock detection perspective would be through the system clock fail logic triggering a trip event through TZ5, but this does have inherent delay as you say. Has the customer tested this in the setup?

Regards,

Allison

0 GR over 2 years ago in reply to Allison Nguyen

Genius 3186 points

Hi Allison,

Thanks for your support.

Allison Nguyen said:
What is the end application here?

application is industrial actuator.

Allison Nguyen said:
The only EPWM path directly from a clock detection perspective would be through the system clock fail logic triggering a trip event through TZ5, but this does have inherent delay as you say. Has the customer tested this in the setup?

I understand EPWM path must be delay by hardware.

My customer had tested and if clock faild, PWM wave might be affect bat customers application.

I will suggest my customer to clock fail detect outside of micro controller.

Best regards,

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28075: If external clock stop, How to instantly stop PWM