DDR3 Swapping byte 0 with byte 3 in 16 bits ddr3 rams

Hi Jonathan,

Refer to the below e2e thread:

http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/717/p/142188/513334.aspx

Best regards,
Pavel

thanks but i saw this tread before  but it does not answer of my question.    I know , i can swap byte 0 and byte1 in the same ram chip.  But can i swap byte 0 (in a 16x ram) with byte 3 (in other 16x ram). 

thanks!!!

Hi Marc,

Just to confirm that I understand the swapping options correctly. 

Could you please confirm that the description below is correct for lane and bit swapping.

Regards

Manie

For a x16 DRAM, a byte lane swap is defined as making ALL of the substitutions below:

      Lower byte lane <=> Upper byte lane

              DQ07:00 <=> DQ15:08

                  LDM <=> UDM

diff pair LDQS, LDQS* <=> diff pair UDQS, UDQS*

In addition, the following bit swaps are allowable for x4, x8, or x16 DDR2 or DDR3 devices:

                    Any of these bits: DQ0, DQ1, DQ2, DQ3, DQ4, DQ5, DQ6, DQ7

may be swapped with any of these bits: DQ0, DQ1, DQ2, DQ3, DQ4, DQ5, DQ6, DQ7

                    Any of these bits: DQ08, DQ09, DQ10, DQ11, DQ12, DQ13, DQ14, DQ15

may be swapped with any of these bits: DQ08, DQ09, DQ10, DQ11, DQ12, DQ13, DQ14, DQ15

Jonathan,

Here is what I found regarding DDR byte swap:

The EMIF data bytes do not have to go to the "same" data bytes on the DDR memory devices, but the entire byte (data bits, data mask and DQS) must go to the same byte on the DDR device.  In other words, it is okay for byte1 of the DDR device to be connected to our device's byte0, but *all* of byte0 needs to go to byte1 of the memory device.

Just keep the entire bytes together and there will be no issue.

Refer also to the below links:

http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/p/160641/660439.aspx

http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/537/t/146893.aspx

http://e2e.ti.com/support/arm/sitara_arm/f/791/t/230862.aspx

EDIT: I will double check with our HW experts and let you know their answer.

BR
Pavel

Thanks !!