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TMS320F280049: Achieving High Resolution Phase Shifting Between 2 Unrelated PWM Channel

Brian Wang0
Expert 5200 points
Part Number: TMS320F280049

Hi team,

Here is a use case from customer:

In F280049, they are trying to achieve high resolution phase shifting between PWM3 and PWM6. According to our PWM sync tree, we cannot directly synchronize PWM6 with PWM3. Here is 2 possible ways we are thinking about.

1. PWM3 triggers DMA to write PWM6 counter. 

The problem for this solution is seems we do not provide a 'HR counter'.

2. PWM3 triggers DMA to write PWM6 SWFSYNC bit and use the HR Phase to achieve shifting.

What is the recommended way to achieve such application from BU side?

Regards,

Brian

  • 0
    TI__Mastermind 24095 points

    Brian,

    Since software is involved the synchronization delay can vary depending on the code execution.
    There is no way to directly control the phase shift with high resolution in software.
    When synchronization is applied in hardware, the TRREM content can be changed to address the phase shift needed.
    I can not think good way of synchronizing these two PWMs at high resolution when you are completely doing via software.
    Also, even the hardware synchronization method, sync pulse is applied only when there is a change in the phase shift.
    If the synchronization is turned on continuously, it could result in jitter. That's a different issue related to synchronization, not directly related to your question.

  • 0 in reply to Subrahmanya
    TI__Expert 5200 points

    Bharathi,

    Thanks for the timely reply.

    So the point is even if customer try to achieve the sync somehow via S/W, since there is S/W delay, the high resolution is actually meaningless.

    If it just from pure technical perspective, is it possbile to trigger the S/W sync via DMA?

    Regards,

    Brian

  • 0 in reply to Brian Wang0
    TI__Mastermind 24095 points

    Brian,

    Yes, Sync can be triggered but not at High resolution, using S/W Sync.