DDR UDQS and LDQS into one DQS controller

Question

I have one x16 memory chip () that has two Data Strobe pairs (UDQS and LDQS), on the other hand, I have arm chip (i.MX6 ULZ) that has one Data Strobe pair (DQS). Is there any way of connecting them, I'm concerned about connecting them together because they are bi-directional. Will a solution like this work? (Just ignore length matching) DDR

Answer 1

According to the datasheet, the part does have 2 DQS pairs (as well as DM and so forth):

Snippet from data sheet

Page 97, pin assignments.

The two sets of DQS probably would be used for 2 8 bit devices, but effectively your 16 bit device is just that anyway. There may be a bit of glue required to use a 16 bit memory, though.

That said, it is possible that a single DQS pair is used for both upper and lower strobes.

The design files for the development board are available if you have an NXP account. Usually pretty easy to set up an account and then you can look at the schematics and see how NXP did the interfacing.

• Hexagonale: these schematics are great source of knowlege, thank You!

Answer 2

As I understand it...

UDQS = Upper byte data strobe (for upper 8 bits)

LDQS = Lower byte data strobe (for lower 8 bits)

So if your DDR3 controller has only one DQS then it only supports an 8-bit data bus. Therefore you can only use 8-bits of your DDR3 memory and must throw away the other 8-bits of bus width.

The chance of your processor only having an x8 DDR3 bus is rare, so I would double check your datasheet, footprint and whether the memory chip you have selected is ideal for this application.

• Peter Smith: The part in question supports 16 bit data
• Hexagonale: Controller supports only x16 memories and has only DQS, it's pretty strange and I don't know how to work with it :/