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

ID 772538
Date 11/18/2024
Public
Document Table of Contents

10.4.3. AXI to Memory Mapping

You can select which region of the memory (bank, bank group, row, column, and chip) to access by selecting the corresponding AXI address.

The default configuration is as follows:

Table 198.  4-Bank-Group case (DDR4, LP5, DDR5)
<MSB   LSB>
Chip Select Chip ID Row Bank Bank Group [1] Column [N:3] Bank Group [0] Column [2:0] Datapath
Table 199.  8-Bank-Group case (DDR5 only)
<MSB   LSB>
Chip Select Chip ID Row Bank Bank Group [2] Column [N:3] Bank Group [1:0] Column [2:0] Datapath

Datapath: For a x32 or wider interface, two bits are allocated to datapath. For a x16 interface, one bit is allocated; this bit should always be set to zero.

Row/Bank/Bank Group/Column: These are allocated a number of address bits based on the requirements of the connected memory type.

Chip Select/Chip ID: These are each one bit wide and are omitted when not using multi-rank or 3DS configurations.

Example: AXI Address mapping for a DDR4 1Gb x8 device, 2 components per rank for a total DQ Width of x16

You can obtain addressing tables from your memory device datasheet. For this example, the following information applies:

Parameter 1 Gb x 8
Bank Group BG[1:0]
Bank Address BA[1:0]
Rows A[15:0]
Columns A[9:0]

The following AXI Address to Memory Mapping table can be constructed.

Memory Address Bits AXI Address Bits
Datapath [0] [0] - Always 0, 1 bit for x16 interfaces
Column [2:0] [3:1]
BG [0] [4]
Column [9:3] [11:5]
BG [1] [12]
BA [1:0] [14:13]
Row [15:0] [30:15]

Using this information, the AXI Address to write to Column 1016 of the Row 0, Bank group 0, Bank 0 is: 0x00000FE0.