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AM335x CK and ADDR_CTRL trace length

Daisuke Maeda
Guru 20205 points

Does each parameter of NO.1 to NO.12 in Table 7-66 on the datasheet indicate the real trace (the etch) length, not horizontal or vertical length?

Best regards,

Daisuke

 

  • 0
    TI__Guru**** 393215 points

    Yes, these are real trace lengths.

  • 0 in reply to Biser Gatchev-XID
    Guru 20205 points

    Hi Biser,

    Thank you for your reply.

    I have an additional question.

    What is "AS"? Does this indicate the length to route down lower than each DDR3 memory?

    For the longest CK and ADDR_CTRL Manhattan distance: "Assuming A8 is the longest, CALM = CACLMY + CACLMX + 300 mils. The extra 300 mils allows for routing down lower than the DDR3 memories and returning up to reach A8."

    If non-A8 is the longest, is the extra 300 mils available?

    Best regards,

    Daisuke

     

  • 0 in reply to Daisuke Maeda
    TI__Guru**** 393215 points

    AS makes sense if you have more than one memory chip and Vtt termination resistors. This is the stub length from the address/control trace to the memory pin. If you use a single memory without Vtt termination you can disregard it.

    The extra 300mil are added to the longest manhattan length, no matter which address/control line it is. This 300mil accounts for the PCB thickness when routing the traces on more than one layer.

  • 0 in reply to Biser Gatchev-XID
    Guru 20205 points

    Hi Biser,

    Thank you for your reply.

    Are NO.6 (AS length) and NO.7 (AS skew) applied to ADDR_CTRL net class only? Are NO.8 (AS+ and AS- length) and NO.9 (AS+ and AS- skew) applied to CK net class only?

    If routing the traces only on one layer, should the extra 300mil not be added?

    Best regards,

    Daisuke

     

  • 0 in reply to Daisuke Maeda
    TI__Guru**** 393215 points

    Daisuke Maeda said:
    Are NO.6 (AS length) and NO.7 (AS skew) applied to ADDR_CTRL net class only? Are NO.8 (AS+ and AS- length) and NO.9 (AS+ and AS- skew) applied to CK net class only?

    Yes, your understanding is correct.

    Daisuke Maeda said:
    If routing the traces only on one layer, should the extra 300mil not be added?

    I don't see how you can route all address/control signals on a single layer. The formula is valid for all cases.

  • 0 in reply to Biser Gatchev-XID
    Guru 20205 points

    Hi Biser,

    Thank you for your reply.

    Best regards,

    Daisuke