• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 2 answers
  • Subscribers 82 subscribers
  • Views 1379 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F280049: question for EPWMXLINK, global load and one-shot load mode

Aki Li
Genius 9855 points
Part Number: TMS320F280049


I am looking into in the configurations of multiple phase topology, so EPWMXLINK, global load and one-shot load mode will be used here. I have a few questions here:

1. EPWMXLINK

  • If using EPWMXLINK among different epwm modules, ie, all CMPA linked to Epwm1's, when a write to CMP1A, the same value will be written to the other CMPxA registers,  within the same CPU cycle, right?  Do the values take effect at this moment only for the shadow registers?

2. Global Load

  • With global load feature enabled, the shadow to active registers transfer will occur within the same clock cycle, right? Whether to enable one shot load mode does not affect it, right?

3. One-Shot Load Mode

  • One-shot load mode is used to make sure the shadow register to active register transfers to occur once with global load scheme. Could you please help share what actual applications will require this? In TIDA-00961, it was mentioned that it is due to the switching frequency could be much higher than the control ISR frequency.

Highly appreciated. 

  • 0
    TI__Guru 52040 points

    1. If you have shadow mode enabled then yes the shadows get updated all with the same value.

    2. Yes the global load mode's job is to ensure they all get updated at the same time.

    3. At higher frequencies, you have need to have a shorter ISR, make sure all registers are updated before the SHADOW to ACTIVE event load occurs. This timing issue is resolved by using global load.

    Nima

  • 0 in reply to Nima Eskandari
    TI__Genius 9855 points

    Nima,

    Thank you for the help.

    Nima Eskandari said:
    3. At higher frequencies, you have need to have a shorter ISR, make sure all registers are updated before the SHADOW to ACTIVE event load occurs. This timing issue is resolved by using global load.

    I am still not quite understand the benefit of the one shot load mode. It can make sure the global load event occur once, but is there any concern/side effect if we let the global load action occur at every selected event,like CNT_ZRO. Could you please help further explain it? 

  • 0 in reply to Aki Li
    TI__Guru 52040 points

    no there is no side effect of doing a global reload at every CNT_ZRO event.

    Nima

  • 0 in reply to Nima Eskandari
    TI__Genius 9855 points

    Nima, 

    Okay, could you please help address the use case for one shot load mode? Thank you.

  • 0 in reply to Aki Li
    TI__Guru 52040 points

    The use case for one shot load is to make sure that all the registers get updated at the same time.

    Typically, user would write to all shadow registers across multiple modules and then apply global load so that the shadow to active loads are initiated. 

    With global load s/w can control the timing of the load occurrence.

  • 0 in reply to Nima Eskandari
    TI__Genius 9855 points

    Nima,

    Sorry, I am still struggling with the global load and  one shot load. As said, global load mode is also update the registers at the same time, I am thinking the below configurations:

    EPWM1 ZERO event is used to sync EPWM2, and EPWM1's registers are set to enable global load at ZERO event, while EPWM2's registers are set to enable global load at sync event. Can the registers of EPWM1 and EPWM2 be updated at the same clock cycle at ZERO event? If so, one shot load mode is not required here.

  • 0 in reply to Aki Li
    TI__Genius 9855 points

    Nima,

    It seems that I figured out why we need one shot load, that it makes sure the global load occurs only after we update all required registers(shawdow). Thus, one shot load is enabled after we update all required registers normally. It helps with variable frequency applications.