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DDR3 for TMS320C6672

Alex Watson
Intellectual 1570 points
Other Parts Discussed in Thread: TMS320C6672

Hello All,

I had the below request and was hoping someone could help me with a recommendation;

I am looking at what memory to use with our TMS320C6672 DSP. The DSP will apparently support  Four off 16Meg x 16 x 8 = 8Gbit total, or maybe it’s Two off 16Meg x 16 x 8 = 4Gbit total, the manuals are ambiguous.

My current thoughts are to use the Micron MT41J128M16JT-125 either 2 off for 32bit or 4 off for 64bit. Can you advise if this is OK?

  • 0
    TI__Mastermind 42545 points

    Hi Alex,

    The C6672 can support either of the configurations that you have suggested. Note that the -125 part can support up to DDR3-1600. The C6672 DDR3 interface is only rated to DDR3-1333. You can still use this device but you can only operate the interface at the slower speed. Please follow all the guidelines in the DDR3 Design Requirements for KeyStone Devices. 

    Regards, Bill

  • 0 in reply to Bill Taboada
    TI__Intellectual 1570 points

    Hi Bill,

    Thank you for your quick response yesterday I really appreciate it and the quality of answer was excellent.

    I was wondering if you would also be able to help me with a second request or help to point me in the right direction;

    When booting the TMS320C6672 in both SRIO and I2C modes bootmode pins 3 and 4 (GPIO 4 and 5) are referred to as ‘reserved’. If they were bought out for later use as GPIO what state should they be pulled to, bearing in mind the following note from the data sheet?

     “Note—If a configuration pin must be routed out from the device and it is not driven (Hi-Z state), the internalpullup/pulldown (IPU/IPD) resistor should not be relied upon. TI recommends the use of an externalpullup/pulldown resistor. For more detailed information on pullup/pulldown resistors and situations inwhich external pullup/pulldown resistors are required, see Section 3.4 ‘‘Pullup/Pulldown Resistors’’ on page 94.”

    I look forward to hearing from you and again thank you for taking the time to offer support yesterday.

    Kind Regards, Alex

  • 0 in reply to Alex Watson
    TI__Intellectual 1570 points

    Hi Bill,

    In addition to the above could I just verify something about your previous post;

    Why is the C1672 DDR3 interface only rated at 1333MHz? The following line is from the April 2013 data sheet

    “For fast access to external memory, this device includes a 64-bit DDR-3 external memory interface (EMIF) running at 1600 MHz” (page 14)

    Any clarification on this would be greatly appreciated as the customer was a bit confused.

    Thank you for the support I look forward to hearing from you soon.

    Kind Regards, Alex

  • 0 in reply to Alex Watson
    TI__Mastermind 42545 points

    Hi Alex, 

    To answer the first question, the official position from TI is that all bootmode pins that are used should be held in a steady-state at the release of RESETFULLz. The internal pulling resistors are only valid for balls connected to a pad without any routing attached. In theory, bootmode 3 and 4 are reserved and shouldn't need to be pulled, however, I am uncomfortable recommending that approach. All testing for these parts include circuity to set the values of these pins during the release of RESETFULLz. My recommendation to customers it that all bootmode pins, used or reserved, should have external pulling resistors or be driven with the bootmode when RESETFULLz is released. 

    As for the second question, usage note 14 in the errata is still active for the C6672. I'll ask the documentation team why this information hasn't been rolled into the data manual. 

    Usage Note 14 DDR3 Performance Limited to 1333MT/s Usage Note

    Revision(s) Affected: 1.0, 2.0
    Details: The DDR3 interface is currently limited to a maximum transfer rate of 1333MT/s. It can be configured to operate at any rate from 800MT/s to 1333MT/s. This coincides with DDR3 clock rates from 400MHz to 666.5MHz.

    Regards, Bill

  • 0 in reply to Bill Taboada
    TI__Intellectual 1570 points

    Hi Bill,

    Thank you for getting back to me I really appreciate it and the answers above are very useful.

    Could I please just clarify if the customer is to pull bootmode pins 3&4 high or low?

    Thank you for your support with these requests it has been very useful and I really appreciate you taking the time to help.

    Kind Regards,

    Alex

  • 0 in reply to Alex Watson
    TI__Mastermind 42545 points

    If they are considered unused, pull them low.

    Regards, Bill

  • 0 in reply to Bill Taboada
    TI__Intellectual 1570 points

    Hi Bill,

    Thank you for your support all of your answers have been very useful.

    Have a great day and thank you again.

    Kind Regards,

    Alex