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ADS7957-Q1: Bihavior after power-on reset

Takumi Suzuki1
Mastermind 8610 points
Part Number: ADS7957-Q1


Hi,

Let me confirm following items about the behavior of ADS7957-Q1.

1) "SDO output data" after power-on rest

I understood that,

 After power-on rest, the device is initialized to "manual mode" and device is ready to wait "CS" falling edge(↓).

   When the 1st "CS" is issued after reset, the SDO outputs "ch0" data of "manual mode". (Frame 1)

   And then the mode register is set to change the mode, for example auto-2 mode, at the 1st "CS". (Frame 1)

   Mux is still set to "ch0" and acquired the data at "Frame 1". 

   In next CS (Frame 2),

   The SDO outputs "ch0" data of "manual mode" and the Mux is set to "ch0" of "auto-2 mode.

   In 3rd CS (Frame 3)

   The SDO outputs "ch0" data of "auto-2 mode" and the Mux is set to "ch1". 

   As a result, after power-on rest, in case of changing auto-2 mode, the "ch0" data is outputed 3 times continuously. 

Is my idea right?

When we program register to change mode at "Frame n", the new ch data of the new mode will be output at "Frame n+2" 

Is this correct?

2) seems to be typo

The following is Figure 54 at page 33.

I suppose the items red marked seem to be typo, 0001 → 0011, auto-1 → auto-2...

How about your idea?

3) mode change

Is it necessary to program mode register 3 times (3 Frames) to change mode?

Just one time is not enough?

4) Invalid data program

If we send invalid data(wrong data) to program, how this device works?

The data will be ignored or something error message will be output from SDO?

This device outputs only AD data ??   

Sorry long question and thank you very much for your support.

Best Regards,

 

 

  • 0
    TI__Expert 5575 points

    Hi Takumi San

    Please my answers to your questions

    1. Yes your understanding is correct.

    After power-on reset device by default operates in manual mode. After first CS falling edge, first SDO data frame is invalid and should be discarded. When you are programming device in either Auto-1 or Auto-2 mode then device continues operation in manual mode- CH0 throughout the programming sequence. Once programmed in desired operating mode (Auto-1/Auto-2) then device ouputs valid conversion result after 2 frames. So lets say you are entering into to auto mode on "N Frame" then data for first channel in that auto mode is available on "N+2 frame"

    2. Yes. It is a typo. It should be updated. Thanks for pointing this out. We will work on getting this corrected.

    3. Lets say you need to operate in to auto-1 mode then you can either program device each time in auto-1 mode or you can say continue operation in existing mode. Mode register setting for continued operation in same mode is given in Table 7

    4. If you send wrong data frame to program then device remains in existing mode. If you send wrong data frame for programming after power-on/Reset then device will be in manual mode.

    I hope this answers your queries.

    Thanks & Regards

    Abhijeet

  • 0 in reply to Abhijeet Godbole
    Mastermind 8610 points

    Hi Abhijeet-san,

    Thank you very much for your reply !

    I understood well.

    But let me confirm the way to keep same mode operating, for sure.

    To stay same(current) mode, for example auto-1 mode, we should do one of following ways.

        - Program mode "auto-1" at every Frame : DI15-12 = 0010

        - Program mode "Continued operation" at every Frame : I15-12 = 0000

          This means equal to set SDI pin hold "low" (=0).

        - Program wrong data : in this case, this wrong data is ignored and then as a result the current mode does not change.

          This is of course not recommended way...

    Is my understanding correct?

    Thank you for your kindenss.

    Best Regards,

  • 0 in reply to Takumi Suzuki1
    TI__Expert 5575 points

    Hi Takumi San

    Yes. Your understanding is correct. Do let me know if you need additional information about this device.

    Thanks & Regards

    Abhijeet

  • 0 in reply to Abhijeet Godbole
    Mastermind 8610 points
    Hi Abhijeet-san,

    Thanks so much for your prompt reply !!

    Regards,