
Chapter 4
Registers
351
24674
Rev. 3.00
April 2003
AMD-8111 HyperTransport I/O Hub Data Sheet
AMD Preliminary Information
0
25
STP
Start of Packet indicates that this is the
fi
rst buffer to be used by the
network controller for this frame. It is used for data chaining buffers. The
STP bit must be set in the
fi
rst buffer of the frame, or the controller skips
over the descriptor and polls the next descriptor(s) until the OWN and
STP bits are set. STP is set by the host and is not changed by the
controller.
End of Packet indicates that this is the last buffer to be used by the
controller for this frame. It is used for data chaining buffers. If both STP
and ENP are set, the frame
fi
ts into one buffer and there is no data
chaining. ENP is set by the host and is not changed by the controller.
Reserved
This bit causes the transmission of the corresponding frame to be
aborted. If the transmitter has not started sending the frame at the time
that the descriptor processing logic encounters the KILL bit, no portion of
the frame is sent. If part of the frame has been sent, the frame is
truncated, and an FCS
fi
eld containing the inverse of the correct CRC is
appended.
Reserved.
Buffer Byte Count is the usable length of the buffer pointed to by this
descriptor, expressed as an unsigned integer. This is the number of
bytes from this buffer that are to be transmitted by the network controller.
This
fi
eld is written by the host and is not changed by the network
controller. There are no minimum buffer size restrictions.
Reserved.
VLAN Tag Control Command
. This
fi
eld contains a command that
causes the transmitter to add, modify, or delete a VLAN tag or to transmit
the frame unaltered.
00 = Transmit the data in the buffer unaltered
01 = Delete the VLAN tag (the 13th through 16th bytes of the frame)
10 = Insert a VLAN tag containing the TCI
fi
eld from the descriptor
11 = Replace the TCI
fi
eld of the frame with TCI data from the descriptor
Tag Control Information
. If the contents of the TCC
fi
eld are 10 or 11,
the controller transmits the contents of the TCI
fi
eld as bytes 15 and 16
of the outgoing frame.
Transmit Buffer Address
. This
fi
eld contains the low order bits of the
address of the Transmit buffer that is associated with this descriptor.
User Space
. Reserved for user de
fi
ned data.
0
24
ENP
0
0
23
22
KILL
0
0
21:16
15:0
BCNT
4
4
31:18
17:16
TCC[1:0]
4
15:0
TCI[15:0]
8
31:0
TBADR[31:0]
0Ch
31:0
USER SPACE
Table 67.
Transmit Descriptor Bit De
fi
nitions (Continued)
Offset
Bit
Name
Description