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AM3874 GPMC Timing Formula

Michi Yamamoto
Intellectual 610 points
Other Parts Discussed in Thread: AM3874

Hi,

I have one question regarding timing formula of GPMC for AM3874.

I analyzed the difference of the both formula between the data sheet and the technical reference manual.

Please see the attched file.

I would like to know which formula for (D) and (E) are correct the data sheet or the technical reference manual.

I understand other formula (K), (L), (E),  (F), (G) and (M). I think that data sheet formula is correct for (K), (L), (E), (F) , (G) and (M).

But I don't know (D) and (E). It is difficult to judge which is correct formula for (D) and (E)? Please let me know.

Best regards,

Michi

  • 0
    TI__Genius 15310 points

    Michi,

    Can you attached the file you mention in your post?

    BR,

    Viet

  • 0 in reply to Viet Dinh
    Intellectual 610 points

    Viet-san,

    Sorry, I missed to attach the file.

    I attached the excel file.

    Please check it. And give me advice.

    5700.GPMC_Timing Formula.xlsx

  • 0 in reply to Michi Yamamoto
    TI__Prodigy 400 points

    Before answering the question I would like to mention to you that these two documents have given information in 2 different contexts.

    DataSheet information :: always give time  from rise edge of the last valid data to BE disable.---------------------------(1)

    TRM: Gives the time from the rise edge of the first valid data to BE disable ---------------------------------------------------(2)

    It is to be noted that as per the programmation of the timing parameters of GPMC, we can not find (2).

    Reason:: For a Write Burst of size = 8. The programmation will be as : AccessTime = 8 , WrCycleTime = 9.

    For such programming, the first data comes after 8 clock cycles, followed by 7 cycles of back to back data( Not counted while Programming WrCycleTime), and then 1 cycle which ends the whole transaction.

     

    Summarizing : TRM information used. Datasheet gives information only if  "D" = time from rise edge of last data of the burst ( for single data transfer this is also first data=last data) to de-activation of the BE/ADV signal.

    Best regards,

    Chaitanya Vaddadi

  • 0 in reply to Chaitanya Vaddadi
    TI__Prodigy 400 points

    Small Typo. Indicated in bold below:

     

    Summarizing : TRM information cannot be used. Datasheet gives information only if  "D" = time from rise edge of last data of the burst ( for single data transfer this is also first data=last data) to de-activation of the BE/ADV signal.

    Best regards,

  • 0 in reply to Chaitanya Vaddadi
    Intellectual 610 points

    Chaitanya-san,

    Thank you for your advice.

    I  understand TRM formula can not be used for time calculation.

    However I am still confused.

    > DataSheet information :: always give time  from rise edge of the last valid data to BE disable.---------------------------(1)

    > TRM: Gives the time from the rise edge of the first valid data to BE disable ---------------------------------------------------(2)

    Regarding (1), is it meaning that "it gives the time from last valid data to the rise edge of GPMC_CLK"?

    And, regarding (2), is it meaning that "it gives the time from the first valid data to the rise edge of GPMC_CLK?

    Please give me more information.

     

    Best regards,

    Michi