Broadcom BCM5722 - Figure 23: Receive Return Ring Memory Architecture Diagram

Programmer’s Guide BCM5722
10/15/07
Broadcom Corporation
Document 5722-PG101-R Page 48
Figure 23: Receive Return Ring Memory Architecture Diagram
Host Memory
1-(64K-1) Bytes
Host Buffer
RX BD
Host
Address
index
type
ip chksum
error flag
reserve
d
opaque
Receive Buffer Descriptor
len
flags
tcp_udp_chsum
vlan tag
Ring Control Block
1st
Host Ring Address
max_len
NIC Ring Address
flags
Receive Ring #1
Receive Ring #16
1st
The ring and gives the length of the rin
g.
and configures the ring. The NIC ring
address is invalid for the receive return ring
Prod
Cons
RCB #1
RCB #16
Status Word
unused
RX Prod #1
RX std cons
RX Prod #2
Unused
Status Block
RX big Cons
RX mini Cons
TX Cons #1
RX Prod #16TX Cons #16
Con
Prod
Mailbox Registers
RX Cons #1
RX Cons #2
RX Cons #16
Note:
The receiver return rings are always
stored in host memory.
Status Block (80 bytes)
Status block resides in the NIC memory
space and is periodically DMA'd to the
host based on the host coalescing
timer.
The NIC is the Producer of the receive
return ring. It increments the internal
producer index to add elements to the ring.