Receive Data PathBCM5718 Programmer’s Guide
Broadcom®
January 29, 2016 • 5718-PG108-R Page 55
Rules Checker
The rules checker examines frames. After a frame has been examined, the appropriate classification bits are
set in the buffer descriptor. The rules checker is part of the RX data path and the frames are classified during
data movement to NIC memory. The following frame positions may be established by the rules checker:
• IP Header Start Pointer
• TCP/UDP Header Start Pointer
• Data Start Pointer
RX List Initiator
The RX List Initiator function activates whenever the receive producer index for any of receive buffer descriptor
(BD) rings is written. This value is located in one of the receive BD producer mailboxes. The host software writes
to the producer mailbox and causes the RX Initiator function to enqueue an internal data structure/request,
which initiates the DMA of one or more new BDs to the NIC. The actual DMAs generated depend on the
comparison of the value of the received BD host producer index mailbox, the NIC copy of the received BD
consumer index, and the local copy of the received BD producer index.
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