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XSNR, XSRD, RTP not in found DDR Data sheet

Thalib
Intellectual 580 points

Hi,

In our custom board we are using MT46H64M16LF mLPDDR and TI DM355 Processor.

As per the TI DDR/mDDR manual to configure the SDTIMR2, following XSNR, XSRD, RTP value should be obtained from DDR Datasheet, It is not found in the Datasheet.

Could you help me in how to fill those registers. 

I have attached the datasheet of DDR for your reference. 

Regards,

Thalib HM

128MB_SDRAM.PDF
  • 0
    TI__Mastermind 27585 points

    The names are slightly different for mDDR:

    T_RASMAX is tRAS (max column in the table)
    T_XSNR and T_XSRD must be programmed equal to tXSR
    T_RTP is not used for mDDR. Only used for DDR2.

    Jeff

  • 0 in reply to jc-ti
    Intellectual 580 points

    Dear Jeff,

     

    Thanks for the answer.

    I need one clarification.In TI DM355 DDR2/mDDR Memory Controller User Manual, in section 4.4 SDRAM Timing Register (SDTIMR) The formula to get register values are below

    T_RFC = (trfc / DDR_CLK) - 1

    T_RP = (trp / DDR_CLK) - 1

    and so on ....

    But In the same manual under 3.2.3 Configuring SDRAM Timing Registers (SDTIMR and SDTIMR2)

    T_RFC = (tRFC × fDDR2/mDDR_CLK) - 1
    T_RP =(tRP × fDDR2/mDDR_CLK) - 1

    Can you please clarify the above. whether it should be divided or multiplied, which one is correct?

  • 0 in reply to Thalib
    TI__Mastermind 27585 points

    Section 4.4 has the note which says DDR_CLK is the period of the DDR_CLK signal. 1/DDR_CLK = fDDR2

    So you can multiply by the frequency or divide by the period and you will get the same result. Performing the wrong operation would always give you 0.

    Jeff