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What is DDR software leveling ?

How it is different from DDR2 and DDR3 ?

Why it is required and important ?

Is there a hardware leveling ?

I have found some explanation here about DDR3 and a general one here but it is not clear for software guys !

There is a seed used for this how this seed is calculated ?

Generally leveling is required to ensure proper timing for read /write operation is that the only purpose??

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What is DDR software leveling ?

It is a method to compensate for the signal propagation delays as a result of different trace length at high frequencies.

How it is different from DDR2 and DDR3 ?

It is just a mechanism that is used for (DDR2 and)? DDR3.

Why it is required and important ?

It is intended for fine tuning the DDR interface. For example to be able to use higher frequencies.

There is a seed used for this how this seed is calculated?

The seed values are the actual values that are used to configure the DDR PHY registers in software. In general, the values depend on DDR3 clock frequency and CK and DQS trace lengths. Texas instruments for example provides an Excel spreadsheet for obtaining the seed values.

Generally leveling is required to ensure proper timing for read/write operation is that the only purpose?

As far as I can tell, yes.

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  • \$\begingroup\$ thanks for answer. I am already using TI spreadsheet for SW leveling but i am more curious about the CK and DQS ?! why those two lines specially as there are too many connection between the processor and the DDR?! \$\endgroup\$ – Abdurahman Oct 23 '13 at 19:17
  • \$\begingroup\$ @Abdurahman: Minimal timing skew between the clock and DQS signals is probably the most critical timing requirement. But I would have to read up on that in detail as well. \$\endgroup\$ – Rev1.0 Oct 23 '13 at 20:10
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    \$\begingroup\$ I will accept the answer for now but updating it with more technical details would be great! thanks \$\endgroup\$ – Abdurahman Oct 23 '13 at 20:16
  • \$\begingroup\$ Is there a hardware leveling ? \$\endgroup\$ – Abdurahman Oct 24 '13 at 11:08

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