Transmit Data Path; Tx Mac; Tx Fifo; Figure 4: Transmit Data Path - Broadcom NetXtreme/NetLink BCM5718 Series Programmer's Manual

BCM5718 Programmer's Guide

Transmit Data Path

TX MAC

The Read DMA engine moves packets from host memory into internal NIC memory (see
entire packet is available, the transmit MAC is activated.
Host Send Producer Rings
TX Data
TX Data
TX Data
TX Data
TX Data
TX Data
TX Data
TX Data
Consumer
Index
Update
The transmit MAC is responsible for the following functions:
• Moving data from NIC internal memory into TX FIFO
• Moving data from TX FIFO to PHY
• Checksum substitutions (not calculation)
• Updating statistics

TX FIFO

The TX FIFO provides elasticity while data is moved from device internal memory to PHY. There are no
programmable settings for the TX FIFO. This FIFO's operation is completely transparent to host software.
Broadcom
®
January 29, 2016 • 5718-PG108-R

Figure 4: Transmit Data Path

NIC Send Ring Cache
DMA
Send BD
Select Send BDs
(SBDs) from Send
Ring
Buffer0
DMA
Buffer1
Buffer2
Buffer3
Buffer4
Buffer5
Transmit Data Path
Figure 4). When the
Tx TX
FIFO MAC
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