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Original question:

ADS8900B: Programming and configuring the control registers

ADS8900B: What is the use of pattern registers?

Venkatesh P17
Intellectual 895 points
Part Number: ADS8900B

Hi TI Team,

 Can you please help me to understand what is the pattern mentioned through DATA_CNTL, DATA_VAL, PATN_LSB, PATN_MID and PATN_MSB? Please explain me with small and quick example.
I think PATN_LSB/MID/MSB reg. are used to fix the output data in a particular patter like round-off, masking some bit kind of works. Correct me if I am wrong.
Thanks,
  • 0
    TI__Mastermind 36170 points
    Hi Venkatesh,

    Yes, DATA_PATN[19:0] is a fixed pattern that can be selected for the output by setting the DATA_VAL bit, per Figure 43 in the datasheet. This can be helpful in testing the digital interface between the ADS8900B and the host controller.

    Regards,
    Keith N.
    Precision ADC Applications
  • 0 in reply to Keith Nicholas
    Intellectual 895 points
    Hi Keith...

    So, if the DATA_VAL=0 then the output is directly streaming from output data register of ADC, if DATA_VAL=1 then the output is from pattern registers with customised pattern.

    In high speed sensing, whether the pattern registers are continuously writing by ODR? Or this is particular value only??

    Can you please help me to understand with a small example?

    Thanks,
  • 0 in reply to Venkatesh P17
    TI__Mastermind 36170 points
    Hi Venkatesh,

    I'm not sure I understand your question.

    Once you set the DATA_VAL bit to 1 in the DAT_CNTL Register, all subsequent readings will be the contents of the PATN registers. This will result in the same pattern on the output on every reading cycle until the DATA_VAL bit is cleared.

    For Example:
    PATN_LSB= 10101010b
    PATN_MID= 11110000b
    PATN_MSB= 00001100b

    ODR = 11001111000010101010xxb where the last 2 bits (xx) depends on the parity setting.

    Regards,
    Keith
  • 0 in reply to Keith Nicholas
    Intellectual 895 points

    Hi Keith,

    I hope I understood your explanation.

    If we set any pattern in pattern register and our DATA_VAL=1b, then our output will be AND'ed with the pattern register and it will stored in ODR. This happens for every sample

    For Example:
    PATN_LSB= 10101010b
    PATN_MID= 11110000b
    PATN_MSB= 00001100b

    and the value equivalent to current sample is

    =               1111 1100 1111 1100 1100b

    Pattern = 1010 1010 1111  0000 1100

    ODR     = 1100 1100  0000 1000 1000xxb

    am I correct?

    Thanks,

  • 0 in reply to Venkatesh P17
    TI__Mastermind 36170 points
    Hi Venkatesh,

    No, this is not correct. There is no AND operation, the conversion result is simply replaced with the pattern value.

    When DATA_VAL=1, ODR = Pattern = 11001111000010101010xxb. Even if the conversion result is constantly changing, for example with an input sine wave, the ODR will always output the fixed PATTERN value with DATA_VAL=1.

    Regards,
    Keith N.