Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public
Document Table of Contents

14.6.1. ECC Structure

You calculate the ECC based on a Hamming code for the corresponding data word length.

The following table shows the memory data size and the Hamming code word length for each of the ECC-protected memories in the HPS as well as the memory type. The Hamming code word length is calculated based on the full data width and whether the memory is byte- or word- addressable.

Table 402.  ECC Bits Required Based on Data Width
Data Bus Width ECC Bits
8 to 15 bits 5
16 to 31 bits 6
32 to 63 bits 7
64 to 127 bits 8
128 to 255 bits 9
256 bits 10

The on-chip RAM is word-addressable. It supports sub-word accesses, however, through a read-modify-write operation. For example, accessing byte 2 of an on-chip RAM word causes a data read of the whole word with ECC. If the word passes the syndrome check, then the byte 2 data is concatenated with the other three bytes of the original data. ECC is recalculated and data is written to memory.

Table 403.  Memory Data Size and Hamming Code Word Length for ECC-Protected Memories
Peripheral Memory Data Size Memory ECC Bits Data Width + ECC Bits Hamming Code Word (length in bits) Type 66
On-chip RAM 64 x 65536 Word-addressable 8 64+8 67 72 Single port
USB 2.0 OTG RAM 35 x 8192 Word-addressable 7 35+7 42 Single port
USB 3.1 Cache RAM 64 x 6608 Word-addressable 8 64+8 72 Simple dual port
USB 3.1 TX RAM 64 x 4720 Word-addressable 8 64+8 72 Simple dual port
USB 3.1 RX RAM 64 x 2832 Word-addressable 8 64+8 72 Simple dual port
XGMAC TX RAM 68 x 2048 Word-addressable 14 68+14 82 Simple dual port
XGMAC RX RAM 68 x 2048 Word-addressable 14 68+14 82 Simple dual port
66 True dual-port memory has two writeable and two readable ports. Simple dual port memory has one write-only port and one read-only port.
67 Uses read-modify-write for subword accesses.