Figure 12: Transmit Ring Data Structure Architecture Diagram - Broadcom NetXtreme/NetLink BCM5718 Series Programmer's Manual

BCM5718 Programmer's Guide

Figure 12: Transmit Ring Data Structure Architecture Diagram

Host Memory
Host Buffer
1-(64K-1) Bytes
Status Block (80 bytes)
The Status block resides in the NIC
memory space and is periodically
DMA'd to the host when the TX/RX
coalescing timers expire, or when the
RX/TX max coalesced frames
thresholds are met. Software can
examine the TX consumer indices in
the status block to determine which
packets have been sent by the
hardware.
Broadcom
®
January 29, 2016 • 5718-PG108-R
Transmit Ring Data Scructure is located in the host (as shown below), and the device will keep a local (not shown) copy of the rings.
Data Structures in the host
Send Buffer Descriptor
Host Address
length flags
rsvd for firmware VLAN tag
Send Host BD
Status Block
Status Word
unused
RX std cons Unused
Unused Unused
TX Cons RX Prod #1
RX Prod #2
RX Prod #3
RX Prod #4
Host Send Ring #1
Cons
1st
RCB
Prod
Mailbox Registers
TX Host Ring Prod
Descriptor Rings
Data Structures kept on-chip
Ring Control Block
Host Ring Address
max_len flags
NIC Ring Address
The mailbox registers reside
on-chip starting at offset 0x300.
Each mailbox register is 64 bits
wide. Writing the lower 32 bits
triggers an event in the HW.
SW updates the TX Host Ring
producer index to indicate that
there are buffer descriptors ready
for the HW to process.
Page 74