Intel® Agilex™ Hard Processor System Technical Reference Manual

ID 683567
Date 2/14/2023
Public

A newer version of this document is available. Customers should click here to go to the newest version.

Document Table of Contents

16.4.2.5.6. Buffer Size Calculations

The driver knows the amount of data to transmit or receive. For transmitting to the card, the internal DMA controller transfers the exact number of bytes from the FIFO buffer, indicated by the buffer size field of the DES1 descriptor field.

If a descriptor is not marked as last (with the LD bit of the DES0 field set to 0) then the corresponding buffer(s) of the descriptor are considered full, and the amount of valid data in a buffer is accurately indicated by its buffer size field. If a descriptor is marked as last, the buffer might or might not be full, as indicated by the buffer size in the DES1 field. The driver is aware of the number of locations that are valid. The driver is expected to ignore the remaining, invalid bytes.