Figure 28: Overview Diagram Of Rx Flow - Broadcom BCM5722 Programmer's Manual

Programmer's Guide
10/15/07
RX D F
ATA LOW
The receive data flow can be summarized in
Return Rings, Mailbox registers, and status block registers are the main areas of the receive data flow.
MailBox Registers
Rcv BD Std Producer Ring Index
Rcv BD Mini Producer Ring Index
Rcv BD Jumbo Producer Ring Index
1
4
Network
The following steps describe the RX flow sequence.
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 BCM5722 Ethernet controller from the host-
based Receive Producer Ring.
3. The BCM5722 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.
6. The BD used for the received packet is DMAed from the BCM5722 Ethernet controller to one of the receive return rings,
and the Receive Return Ring Producer Index register in the host status block is updated by the BCM5722 Ethernet
controller.
Document 5722-PG101-R
D
IAGRAM
Figure 28. The Receive Producer Ring, Receive Buffer Descriptors, Receive
Buffer Descriptor points
To free RX buffer in host
BD n
BCM570X
Family
5
Host Memory

Figure 28: Overview Diagram of RX Flow

Bro adco m Co rp or atio n
Standard, Mini, and Jumbo Producer
Rings In Host Memory
2
Status Block
status word
3
rcv std cons
unused
TX cons #1
Receive Return Rings 1-16 in
6
BD n
Used Buffer Descriptor points to host
memory where packet was copied
unused
rcv jbo cons
rcv min cons
RX prod #1
host memory
RX Data Flow Diagram
BCM5722
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