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SDOFST, error in document expression?

Anonymous
Anonymous

Hi All,

 

I have a question on SDOFST register of 643x VPFE, on page 50 of document SPRU977a.

                         

 

                                                           

There are several fields in SDOFST and let’s take a look at LOFTS0:
“offset, in lines, between even lines on even fields (field 0)"
According to this and the bottom of the page, offset between even lines should be two lines.

 

By examining Fig. 20, one actually finds (only four lines are shown but we can infer from them arrangement of the following lines) that the offset between even lines are four lines.

 

Is this a mistake in expression? Because if we refer to page 132 where SDOFST fields are explained, LOFTS0 is “line offset values of even lines and even field ID=0”, rather than “between”.

                           

                                               

By “between”, we mean between line (2k-2, 2k).
By “of”, we can either mean between (2k-2, 2k), or (2k-1, 2k).
Therefore although the use “of” still has ambiguity, its second interpretation makes sense.

 

Is this a mistake in the document's expression (especially with “between”)?

 


Sincerely,
Zheng

 

  • 0
    TI__Prodigy 140 points

    Zheng,

    I am not sure of the difference in the "of" or "between". But here is how the logic works.

    On the start of a new field if it is odd then we take the value of the FOFST value and multiply it times the stride and add it to the address in the SDR_ADDR register.

    When we reach the end of a line we look at the LOFSTX to determin what to multiply the stride to and add that to the start address of the current line. So in your case you would expect the stride to be +4 between even lines because you have an even and odd offset both of +2 so +2 +2 = +4.

    Regards,

    David Smith

  • Anonymous
    0 Anonymous in reply to David-MCAD Smith

    Dear David,

     

    I think this is the correct answer. My doubt is resolved.

     

     

    Thanks,

    Zheng