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TMS570LS3137: ADC Continuous Conversion Mode

li qunxiong
Intellectual 335 points

Part Number: TMS570LS3137

Hello,

In the manual,there are two different versions of continuous conversion.

one is If Group1 conversions are ongoing in continuous conversion mode and Group2 conversion is requested, then the ADC will complete converting the current channel for Group1 and switch over to converting channels selected in Group2.

The other is the channels 0, 2, 4, and 6 are selected for conversion in Group1, now in continuousconversion mode. When the Group1 gets serviced, the ADC will complete conversions for channels 0, 2,
4, and 6, and then look to service the Event Group or the Group2.

So which one is right?Wait for the current channel conversion to complete, or wait for all channel conversion to complete?

Thanks.

  • 0
    TI__Guru**** 199216 points

    Hi Qunxiong,

    Both statements are correct.

    Let me clarify the priority of ADC groups:

    The priority of groups is (from highest priority to lowest priority):

    1. Event (EVT)

    2. Group 1 (G1)

    3. Group 2 (G2)

    If an event group conversion is active (single conversion and FRZ EV = 0) and group 2 and group 1 conversions are requested, then when the event group is finished, group 1 is converted then group 2 is converted.

    If group 1 is active (continuous conversion and FRZ G1 = 0) and group 2 conversion is requested, when the current conversion of group 1 is finished, group 2 is converted. The explicit conversion request of group 2 has higher priority than the pending continuous conversion request of group 1.

    In continuous conversion mode, the conversion takes place as specified by the priority. Continuous conversion mode acts like a continually pending group conversion request with the exception that the ADC can distinguish explicit group conversion requests (the explicit group conversion request is triggered by writing to the G1 or G2 group select register or by a valid edge on the ADEVT pin) from the continuous request. The ADC module converts explicit group requests with higher priority than a pending continuous conversion.

    This is an example of conversion sequence using the three groups:

  • 0 in reply to QJ Wang
    Intellectual 335 points

    Hi QJ Wang,

    Do you have the example of conversion sequence using the three groups that 2 groups continuous conversion 1 group single conversion,can you post the sequence picture?

    Thanks.

  • 0 in reply to li qunxiong
    TI__Guru**** 199216 points

    I don't have a diagram for 2 continuous conversion groups and 1 single conversion group. 

  • 0 in reply to QJ Wang
    Intellectual 335 points

    Can all 3 groups be frozen during conversion?

  • 0 in reply to li qunxiong
    TI__Guru**** 199216 points

    The "frozen" is to allow the ADC to freeze the higher priority conversion group's conversion whenever there is a request for conversion in another low-priority group.

    Yes, you can enable "freeze" for all the three conversion groups. Why do you want to enable this feature for the Group 2 which has the lowest-priority?