SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
The DDR controller supports byte lane swapping on the board or a DIMM for better timing or routing. In most cases, this swapping is invisible to the user as data byte lanes are swapped when data is being written, and then unswapped as data is read. However, mode register reads does not un-swap the data. Therefore, the user must be aware of the location of the 0th byte of the data in order to process the information from the mode registers correctly.
Whether byte lane swapping is used or not, the user must program the following fields:
Unique parameters are provided for each chip select to allow for different byte swapping on each chip select. Each field contains one bit for each byte of the memory data bus. If a device is not being used, the DEVICEx_BYTE0_CSy field should be programmed to 0h, but if the device is being used, then only one bit of the DEVICEx_BYTE0_CSy field should be set to 1h.