DDR3 issue in iMX6Q board.

[Rabiammal]

We have connected 4 DDR3 chips to iMX6 processor. The below issue occurs in only one board.

Using JTAG we came to know that the failure is occurring in 0x400F0083 address. If I write 0x A5A5A5A5 to that address, Iam getting back as 0x85A5A5A5. sometimes if I write 0x85A5A5A5, iam getting back as 0xA5A5A5A5. i.e. 29th bit is having the issue.

DDR Address space: 0x10000000 to 0x4FFFFFFF. (256MByte*4Chips = 1GByte)

Each chip is organized as 16Mbit x 16 I/Os x 8 bank devices and placement of the 4 chips are, 2 chips at the top and remaining 2 at the bottom of the SOM.

Also I have gone through the 44.4.4 MMDC Address Space in Document of i.mx6dq and found the following information in our case,

1. chip select : Using only CS0 and CS1 is DNP.
2.MDMISC[DDR_4_BANK]— 8 banks in the DDR device.
3.MDCTL[DSIZ]— DDR data bus width of x64.
4.MDMISC[BI]— Bank interleaving is on.
5.MDCTL[COL]— Column size of the DDR device is 10.
6.MDCTL[ROW]— Row size of the DDR device is 14.
7.MDASP[CS0_END] is 0010_0111 (0x27).
8.Address mirroring enabled.

We would like to know which DDR out of 4 is having the issue?

And also using the schematic, we got the below info
Data Lines D0 -D15 connected to DDR1
Data Lines D16 -D31 connected to DDR2
Data Lines D32 -D47 connected to DDR3
Data Lines D48 -D63 connected to DDR4

Based on the above information , we would like to know Which DDR is having the issue.
We would like to replace that chip alone for resolving the issue.
Please help us in finding the DDR address(0x400F0083) specified lies in which DDR chip?
Note: The issue is found in only board out of 30K board. Hence can confirm that PCB Layout is proper.

[art]

Most likely, this is DDR4. However, to confirm this, try with the byte-wide (not 32-bit wide) accesses on the addresses from 0x400F0080 to 0x400F0087. You should find the issue (flipping bit) on the 0x400F0086 address. Or, try with 32-bit wide accesses on the addresses 0x400F0080 and 0x400F0084. Can you see any flipping bit here?

Have a great day,
Artur

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