External Memory Interfaces Intel Agilex® 7 M-Series FPGA IP User Guide

ID 772538
Date 6/26/2023
Public

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6.3.5.6.1. DDR4 Byte Lane Swapping

The data lane can be swapped when the byte-lanes are utilized as DQ/DQS pins. Byte lane swapping on utilized lanes is allowed when you swap all the DQ/DQS/DM/DBI pins in the same byte lane with the other utilized byte lane.

The rules for swapping DQ byte lane are as follows:

  • You can only swap between utilized DQ lanes.
  • You cannot swap a DQ lane with an AC lane.
  • You cannot swap a DQ lane with an ECC lane when out-of-band ECC is enabled. For x40 interfaces, the highest-indexed DQ byte lane cannot be swapped.
  • Additional restrictions apply when you use a x16 memory component:
    • You must place DQ group 0 and DQ group 1 on adjacent byte lanes, unless they are separated by AC Lanes. These 2 groups must be connected to the same x16 memory component.
    • You must place DQ group 2 and DQ group 3 on adjacent byte lanes, unless they are separated by AC Lanes. These 2 groups must be connected to the same x16 memory component.
    • If you use only one byte of the x16 memory component, you must use only the lower byte of the memory component.
Table 79.  Byte Lane Swapping
Address/Command Scheme Data Width usage BL7 [P95:P84] BL6 [P83:P72] BL5 [P71:P60] BL4 [P59:P48] BL3 [P47:P36] BL2 [P35:P24] BL1 [P23:P12] BL0 [P11:P0]
Scheme 2 DDR4 x32 + ECC DQ[ECC] DQ[3] DQ[2] DQ[1] AC2 AC1 AC0 DQ[0]
Scheme 2 DDR4 x40 DQ[4] DQ[3] DQ[2] DQ[1] AC2 AC1 AC0 DQ[0]

Example 1: DDR4 x 32 +ECC implemented with AC Scheme 2

BL7 is used as ECC DQ lane, while Lane 0, 4, 5 and 6 are used DQ lanes. Byte lane swapping between BL0,4,5,6 is allowed.

Example 2: DDR4 x 40 implemented with AC Scheme 2

BL0,4,5,6,7 are used as DQ lanes. Byte lane swapping between BL0,4,5,6 is allowed. The highest-index DQ byte lane (that is, DQ[4]), cannot be swapped and must be placed at BL7.