Figure 30: Relationships Between All Components Of A Send Ring; Figure 31: Max_Len Field In Ring Control Block - Broadcom BCM5722 Programmer's Manual

BCM5722
Figure 30 illustrates the relationships between all the components of a send ring.
Send
RCB
Consumer
Producer

Figure 30: Relationships Between All Components of a Send Ring

R C B
ING ONTROL LOCK
The Send Ring RCB contains a pointer to the first Send BD in the device and host memory, number of send BDs in the ring,
and control flags (see "Send Rings" on page 74
as required by the BCM5722 Ethernet controller. The RCBs of the send rings are located in the device Miscellaneous
Memory Region at offset 0x0100.
The devices support a host based send ring. The Send BDs of the host based Send Ring will be bus-mastered from host
memory into device local memory. The device driver will program the BDs directly in its memory space and avoid
programmed I/O to the MAC. The Max_Len field in the RCB (see
Send Ring. This field can be programmed to either 32, 64, 128, 256, or 512.
1st Ring Element
Page 75 Send Rings
Send BD 1
Send BD 2
Send BD 3
Send BD 4
Send BD 5
Send BD 6
Send BD 7
Send BD 8
Send BD 512
for a full discussion of the send RCB). All the fields are in big-endian ordering
512th Ring Element
1st

Figure 31: Max_Len Field in Ring Control Block

Bro adco m C orp or atio n
Buffer
Buffer
Figure 31) indicates the maximum number of BDs in the
Host Send Ring Control Block
Offset 32
0x00
0x04
0x08
Max_Len
0x0C
Programmer's Guide
10/15/07
Buffer
16 15 0
Host Ring Address
Flags
NIC Ring Address
Document 5722-PG101-R