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DDR2 Drive Strength - DM6467T

Andrew Muehlfeld
Intellectual 720 points

Section 7.10.2.9 "DDR2 Signal Termination" of the datasheet for DM6467T, states: "When no termination is used on data lines (0 Ωs), the DDR2 devices must be programmed to operate in 60% strength mode."  We have chosen not to use series termination resistors.  How do we set the DDR2 module to 60% strength mode?

 

My best guess is to set register SDBCR[18] "DDRDRIVE" to 1, in UBL, but that's not a clear mapping to 60%.  Can someone confirm, or provide the correct method?

 

Thanks.

  • 0
    TI__Guru 64460 points

    I believe this is intended to mean the actual DRAM device drive strength.  Taking a look at an example DDR2 datasheet, the output drive strength, when in the reduced mode is between 45 and 60 percent.

    Table 13 in the DDR2 Memory Controller User's Guide provides confirmation that the DDRDRIVE control bit is associated with the appropriate A1 address line in a EMRS command to the DRAM device.  This bit is associated with ODS (Output Drive Strength) in the DRAM EMR register.