Table 71: Send Buffer Descriptor (Little-Endian 32-Bit Format) With No Swapping; Table 72: Send Buffer Descriptor (Little-Endian 32-Bit Format) With Word Swapping; Table 73: Send Buffer Descriptor (Big-Endian 32-Bit Format) With Byte Swapping - Broadcom BCM5722 Programmer's Manual

Programmer's Guide
10/15/07
Word Swap Non-Frame Data = 0 and Byte Swap Non-Frame Data = 0
This would require the software to use the following little-endian data structure on the host:

Table 71: Send Buffer Descriptor (Little-Endian 32-Bit format) with No Swapping

Byte #
Bit # 31
MSB
MSB
In this case, the data structure takes on a slightly new format because the words have been swapped.
Word Swap Non-Frame Data = 1 and Byte Swap Non-Frame Data = 0
This would require the software to use the following little-endian data structure on the host:

Table 72: Send Buffer Descriptor (Little-Endian 32-Bit format) with Word Swapping

Byte #
Bit # 31
MSB
MSB
The disadvantage of this approach is if the host operating system supported a 64-bit data type for a physical address, the
host device driver would have to swap the two 32-bit words that comprise the 64-bit address that the host operating system
used.
Word Swap Non-Frame Data = 0 and Byte Swap Non-Frame Data = 1
This requires the software to use the following big-endian data structure on the host:

Table 73: Send Buffer Descriptor (Big-Endian 32-bit format) with Byte Swapping

Byte #
Bit # 31
MSB
MSB
Document 5722-PG101-R
3 2
Reserved
Length
3
Length
Reserved
0
Reserved
Length
Bro adco m Co rp or atio n
1
16 15
Host Address
LSB
2 1
16 15
Host Address
LSB
1 2
16 15
Host Address
LSB
Endian Control (Byte and Word Swapping)
BCM5722
0
0
LSB
VLAN
Flags
0
0
LSB
Flags
VLAN
3
0
LSB
VLAN
Flags
0x00
0x04
0x08
0x0C
0x00
0x04
0x08
0x0C
0x00
0x04
0x08
0x0C
Page 150