RX Data Flow Diagram
BCM5718 Programmer’s Guide
Broadcom
®
January 29, 2016 • 5718-PG108-R
Page 100
RX Data Flow Diagram
The receive data flow can be summarized in
. The Receive Producer Ring, Receive Buffer Descriptors,
Receive Return Rings, Mailbox registers, and status block registers are the main areas of the receive data flow.
Figure 17: Overview Diagram of RX Flow
The RX flow sequence is as follows:
1.
The host software updates a Receive Producer Ring Index in the Mailbox registers.
2.
A receive BD or series of BDs with the corresponding index is DMAed to the Ethernet controller from the
host-based Receive Producer Ring.
3.
The Ethernet controller updates the Receive Consumer Index in the Host Block register and stores copy of
the BD.
4.
A valid Ethernet packet is received from the network into the device.
5.
The Ethernet packet is DMAed to host memory using a BD previously DMAed from a Receive Producer
Ring.
MailBox Registers
status word
rcv std cons
unused
unused
unused
unused
Status Block
Standard and Jumbo Producer Rings
In Host Memory
BD n
Buffer Descriptor points
to free RX buffer in host
TX cons #1
RX prod #1
Receive Return Rings in
host memory
BD n
Used Buffer Descriptor points to host
memory where packet was copied
1
2
3
4
6
5
Host Memory
Network
Rcv BD Std Producer Ring Index
BCM570X
Family