Broadcom BCM5722 - Figure 4: Receive Data Path; Receive Data Path; RX Engine; Rx Fifo

BCM5722 Programmer’s Guide
10/15/07
Broadcom Corporation
Page 15 Receive Data Path Document 5722-PG101-R
RECEIVE DATA PATH
RX ENGINE
The receive engine (see Figure 4) activates whenever a packet arrives from the PHY.
Figure 4: Receive Data Path
The receive engine performs the following four functions:
• Moves the data from the PHY to an internal FIFO
• Moves the data from the FIFO to NIC internal memory
• Classifies the frame and checks it for rules matches
• Performs the offloaded checksum calculations
RX FIFO
The RX FIFO provides elasticity while data is read from PHY transceiver and written into internal memory. There are no
programmable settings for the RX FIFO. This FIFO’s operation is completely transparent to host software.
RX
Engine
Rules Checker
Rx
FIFO
Frame
Buffers
Empty BD
List
Placement
Selector
Lists
NIC RX Producer Ring
Std
Host RX
Return
Rings
Full BD
List
Initiator
1
2
3
4
Rx Return BD Rx Return BD Rx Return BD Rx Return BD Rx Return BD
Rx Return BD Rx Return BD Rx Return BD Rx Return BD Rx Return BD
Rx Return BD Rx Return BD Rx Return BD Rx Return BD Rx Return BD
Rx Return BD Rx Return BD Rx Return BD Rx Return BD Rx Return BD
1
2
3
4
Priority
Selector
Host RX Producer Rin
g
DMA
DMA