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TMS320F28034: PWM sync delay

Jordan Zhou
Genius 10310 points
Part Number: TMS320F28034


Hi,

For type 1 and later PWM modules, there's 1 or 2 clock delay when sync:

My questions are:

1) The delay is between PWM1 and PWM2. What about PWM2, PWM3 and PWM4, are there any delay between them?

2) We'd like to sync 3 PWM modules without any delay, how can we do?

Another issue about sequence between shadow load and compare.

In our application, shadow load is used for CMPA, when CTR=Zero. In up-down mode, when CTR decreased to zero, TWO actions will be done: one is shadow load CMPA, the other is compare CTR and CMPA. What's the sequence of these two actions? Who will be the first? Sometimes, we'd like to set the CMPA to zero by shadow load, and CTR=CMPA=Zero, the AQ works immediately, High or Low.

Thanks a lot.

Br, Jordan

  • 0
    TI__Mastermind 42195 points

    Jordan, 

    1. The delay will only be between PWM1 and PWM2. Between PWM2, PWM3, and PWM4 will be 0.
    2. To sync 3 PWMs you should use a master PWM provide the sync pulse, configure the second PWM to pass through the sync signal to the third PWM. You will need to set TBPHS for the second PWM and third PWM. The delay can change with configuration, the easiest way to find out what value should be inserted into the TBPHS register of the slave PWMs is to sync any two PWMs and then adjust TBPHS  of all slave PWMs.

    When using this device in Up-Down count mode if you use shadow loads to update CMPA from a value >0 to 0 then you will have no issues. When you increase your CMPA value from 0 to a value >0 the CMPA value will be missed for one PWM period. If you would like to force the PWMs output during this period we suggest that you should use the Action Qualifier. 

    Regards,
    Cody