AM335x CK and ADDR_CTRL trace length

Daisuke Maeda

Guru 20395 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

over 11 years ago

0 Biser Gatchev-XID over 11 years ago

TI__Guru**** 393215 points

Yes, these are real trace lengths.

0 Daisuke Maeda over 11 years ago in reply to Biser Gatchev-XID

Guru 20395 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 Biser Gatchev-XID over 11 years ago 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 Daisuke Maeda over 11 years ago in reply to Biser Gatchev-XID

Guru 20395 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 Biser Gatchev-XID over 11 years ago 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 Daisuke Maeda over 11 years ago in reply to Biser Gatchev-XID

Guru 20395 points

Hi Biser,

Thank you for your reply.

Best regards,

Daisuke

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AM335x CK and ADDR_CTRL trace length