Data Sheet

Inline Functions—Ethernet Controller I210
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latency interrupt (associated with the relevant receive queue) once the amount of free descriptors is
less or equal than the threshold. The threshold is defined in 16 descriptors granularity per queue in the
SRRCTL[n].RDMTS field.
7.1.5 Header Splitting and Replication
7.1.5.1 Purpose
This feature consists of splitting or replicating packet's header to a different memory space. This helps
the host to fetch headers only for processing: headers are replicated through a regular snoop
transaction in order to be processed by the host CPU. It is recommended to perform this transaction
with the DCA feature enabled (see Section 8.13) or in conjunction with a software-prefetch.
The packet (header and payload) is stored in memory through a (optionally) non-snoop transaction.
Later, a transaction moves the payload from the software device driver buffer to application memory or
it is moved using a normal memory copy operation.
The I210 supports header splitting in several modes:
• Legacy mode: legacy descriptors are used; headers and payloads are not split.
• Advanced mode, no split: advanced descriptors are in use; header and payload are not split.
• Advanced mode, split: advanced descriptors are in use; header and payload are split to different
buffers. If the packet cannot be split, only the packet buffer is used.
• Advanced mode, replication: advanced descriptors are in use; header is replicated in a separate
buffer and also in a payload buffer.
• Advanced mode, replication, conditioned by packet size: advanced descriptors are in use;
replication is performed only if the packet is larger than the header buffer size.