External Memory Interfaces (EMIF) IP User Guide: Agilex™ 3 FPGAs and SoCs

ID 847458
Date 4/24/2025
Public
Document Table of Contents

A.1.3.1. Narrow Read Transfer Support

Narrow Read Transfer Support

Narrow read transfer happens when the AXI master generates a read data transfer that is narrower than its data bus width. For example, for a 256-bit AXI data bus, a narrow read transfer happens when ARSIZE is less than 5.

Unaligned Memory Access

Unaligned memory access is not supported on Agilex™ 5 EMIF interfaces. For Fabric EMIF, unaligned memory access is not supported in Fabric Direct Access Mode.

For HPS EMIF, unaligned memory access is not supported on the F2SDRAM Bridge. Unaligned memory access happens when the ARADDR/AWADDR is specified with a value that is not a multiple of the data bus width (in bytes).

The following table shows the AWADDR/ARADDR requirement for aligned memory access in Fabric EMIF and HPS EMIF.

Table 59.  AWADDR/ARADDR Requirement for Aligned Memory Access
category AXI Data Width (Bits) AXI Data Width (Bytes) AWADDR/ARADDR for Aligned Access
Fabric EMIF-Direct Access Mode 256 32 32n
HPS EMIF - F2SDRAM 64 8 8n
HPS EMIF - F2SDRAM 128 16 16n
HPS EMIF - F2SDRAM 256 32 32n
Note: n is an integer value equal to or greater than 0.

You will get a data error if you perform unaligned memory access on the EMIF interfaces.