AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 244

• Manufacturer Part Number: AM79C976
• Description: PCnet-PRO 10/100 Mbps PCI Ethernet Controller
• Manufacturer: Advanced Micro Devices

244
Offset
0Ch
1Ch
10h
14h
18h
0
4
4
4
8
31-18
17-16
15-0
15-0
31-0
31-0
31-0
31-0
31-0
31-0
Bit
TBADR[63:32]
USER SPACE
USER SPACE
USER SPACE
TBADR[31:0]
TCC[1:0]
TCI[15:0]
Name
BCNT
Buffer Byte Count is the usable length of the buffer pointed to by this descriptor,
expressed as the two’s complement of the length of the buffer. This is the number of
bytes from this buffer that will be transmitted by the Am79C976 controller. This field is
written by the host and is not changed by the Am79C976 controller. There are no
minimum buffer size restrictions.
Reserved.
VLAN Tag Control Command. This field 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 field from the descriptor
11 = Replace the TCI field of the frame with TCI data from the descriptor
Tag Control Information. If the contents of the TCC field are 10 or 11, the controller
will transmit the contents of the TCI field as bytes 15 and 16 of the outgoing frame.
Transmit Buffer Address. This field contains the low order bits of the address of the
Transmit buffer that is associated with this descriptor.
Transmit Buffer Address. This field contains the high order bits of the address of the
Transmit buffer that is associated with this descriptor.
Reserved.
User Space. Reserved for user defined data.
User Space. Reserved for user defined data.
User Space. Reserved for user defined data.
P R E L I M I N A R Y
Am79C976
Description
8/01/00