Broadcom BCM5722 - Figure 8: Sample Traffic Flow with ISO and Normal Data Packets

Programmer’s Guide BCM5722
10/15/07
Broadcom Corporation
Document 5722-PG101-R Transmit Data Path Page 22
Data/ISO Mixed Transmit Packet Traffic Example
Figure 8 illustrates a sample traffic flow scenario of a mixture of isochronous packets and normal data best-effort traffic
packets.
Figure 8: Sample Traffic Flow with ISO and Normal Data Packets
To support the additional ISO SBD, the following resources are added or modified for the BCM5906 as compared to non-ISO
NetXtreme/NetLink controllers:
• The 64 on-chip SBDs are divided into two groups of 32 SBDs, with the lower 32 SBDs for the normal Data SBD and the
upper 32 SBDs for the ISO SBD.
• The Send RCB (Ring Control Block) now specifies both the Data SBD and the ISO SBD in the following manner:
The Host Ring address for the ISO SBD is defined to start at 512 BDs above the Data SBD in the host memory. Since
each SBD is 16 bytes, the Host Ring address for the ISO SBD starts at the Host Ring address defined in RCB + 0x2000.
The ring size defined in the RCB applies to both the Data SBD and ISO SBD.
• The Send Ring Producer Index for the ISO SBD has been added at register offset 0x5908. The host driver updates this
mailbox register when there is a new ISO packet available.
• The Send Ring Consumer Index for the ISO SBD has been added at register offset 0x3CC0. Hardware updates this
mailbox register when an ISO packet has been sent to the DMA controller.
• Offset 0x16 in the Status block now contains the ISO SBD consumer index, as shown in Table 7.
ISO Data Data ISO Data
100us
ISO
225us 360us
Data
Local Network
Clock
125us
64 Bytes
125us
64 Bytes
125us
64 Bytes
ISO SBD
Ring
130
Bytes
64 Bytes
64 Bytes
Data SBD
Ring
1500 Bytes