External Memory Interfaces (EMIF) IP User Guide: Agilex™ 5 FPGAs and SoCs

ID 817467
Date 11/18/2024
Public
Document Table of Contents

7.5.5.1. DDR5 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 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.
  • For multi-channel configuration, you can only swap DQ lanes of the same channel.
  • 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 177.  Byte Lane Swapping
Address/Command Scheme Data Width per Channel 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 1 DDR5 x32 GPIO GPIO DQ[3] P DQ[2] P AC1 P AC0 P DQ[0] P DQ[1] P
Scheme 1 DDR5 x32+ ECC GPIO DQ[ECC] P DQ[3] P DQ[2] P AC1 P AC0 P DQ[0] P DQ[1] P
Scheme 1 DDR5 2x16 DQ[1] S DQ[0] S AC1 S AC0 S AC1 P AC0 P DQ[0] P DQ[1] P
Note:
  • P = Primary controller.
  • S = Secondary controller.

Example 1: DDR5 x32

BL0, 1, 4, 5 are used as DQ lanes. Byte lane swapping is allowed.

Example 2: DDR5 x32 + ECC

BL6 is used as ECC DQ lane, while BL0, 1, 4, and 5 are used as DQ lanes. Byte lane swapping is allowed on BL0, 1, 4, and 5 only.

Example 3: DDR5 2 x16

For multi-channel configuration, you can only swap DQ lanes of the same channel.

BL0 and BL1 are used as DQ lanes for one channel. Byte lane swapping is allowed on BL0 and BL1.

BL6 and BL7 are used as DQ lanes for another channel. Byte lane swapping is allowed on BL6 and BL7.