External Memory Interface Handbook Volume 3: Reference Material

ID 683841
Date 7/24/2019
Public
Document Table of Contents

8.2. Avalon-MM and Memory Data Width

The following table lists the data width ratio between the memory interface and the Avalon-MM interface.

The half-rate controller does not support burst-of-2 devices because it under-uses the available memory bandwidth. Regardless of full or half-rate decision and the device burst length, the Avalon-MM interface must supply all the data for the entire memory burst in a single clock cycle. Therefore the Avalon-MM data width of the full-rate controller with burst-of-4 devices is four times the memory data width. For width-expanded configurations, the data width is further multiplied by the expansion factor (not shown in table 5-1 and 5-2).

Table 101.  Data Width Ratio

Memory Burst Length

Half-Rate Designs

Full-Rate Designs

QDR II 2-word burst

No Support

2:1

QDR II, QDR II+, and QDR II+ Extreme 4-word burst

4:1

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