Send Buffer Descriptors; Table 12: Send Buffer Descriptors Format; Table 13: Defined Flags For Send Buffer Descriptors - Broadcom BCM5722 Programmer's Manual

Programmer's Guide
10/15/07

Send Buffer Descriptors

The format of an individual send buffer descriptor is shown in
Offset (Bytes) 31
0x00
0x04
0x08
0x0c
The fields are defined as follows:
The Host Address field contains the 64-bit host address of the buffer that the descriptor points to. A length of 0 indicates
•
that the descriptor does not have a buffer associated with it.
• The Flags field contains bits flags that contain control information for the device for transmitting the packets. The
defined flags are listed in
For BCM5906/BCM5906M, 0x0C[31:16] contains the 16-bit Launch Time for Isochronous (ISO) send buffer descriptors.
Bits Name
0 TCP_UDP_CKSUM
1 IP_CKSUM
2 PACKET_END
5:3 Reserved
a
6 VLAN_TAG
7 COAL_NOW
8 CPU_PRE_DMA
9 CPU_POST_DMA
10 Tx Time-Sync packet
(BCM5906, BCM5906M
ISO send BD only.
Reserved (all others)
Document 5722-PG101-R

Table 12: Send Buffer Descriptors Format

Length [15:0]
HdrLen [4:0] MSS [10:0]
Table 13.

Table 13: Defined Flags for Send Buffer Descriptors

Description
a
If set to 1, the controller replaces the TCP/UDP checksum field of TCP/UDP packets with
the hardware calculated TCP/UDP checksum for the packet associated with this
descriptor.
If set to 1, the controller replaces the IPv4 checksum field of TCP/UDP packets over IPv4
with the hardware calculated IPv4 checksum for the packet associated with this
descriptor. This bit should only be set in the descriptor that points to the buffer that
contains the IPv4 header. It is assumed that the IPv4 header is contained in a single
buffer.
If set to 1, the packet ends with the data in the buffer pointed to by this descriptor.
Should be set to 0.
If set to 1, the device inserts an IEEE 802.1Q VLAN tag into the packet. The 16-bit TCI
(Tag Control Information) field of four byte VLAN tag comes from the VLAN Tag field in
the descriptor.
If set to 1, the device immediately updates the Send Consumer Index after the buffer
associated with this descriptor has been transferred via DMA to NIC memory from host
memory. An interrupt may or may not be generated according to the state of the interrupt
avoidance mechanisms. If this bit is set to 0, then the Consumer Index is only updated
as soon as one of the host interrupt coalescing conditions has been met.
If set to 1, the controller's internal CPU is required to act upon the packet before the
packet is given to the internal Send Data Initiator state machine. Normally this bit should
be set to 0.
a
If set to 1, the controller's internal CPU is required to act upon the packet before the
packet is given to the internal Send Data Completion state machine. Normally this bit
should be set to 0.
If set to 1, indicates that this is a time-sync packet used for Isochronous packet flow in
the BCM5906 device family.
Bro adco m Co rp or atio n
Table 12.
16 15
Host Address [63:0]
Flags [15] HdrLen [7:5] Flags [11:0]
BCM5722
VLAN Tag
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