AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 238

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

Transmit Descriptors
When SWSTYLE (BCR20, bits 7-0) is set to 0, the soft-
ware structures are defined to be 16 bits wide, and
transmit descriptors look like Table 110.
When SWSTYLE is set to 2, the software structures
are defined to be 32 bits wide, and transmit descriptors
look like Table 111.
When SWSTYLE is set to 3, then the software struc-
tures are defined to be 32 bits wide, and transmit de-
scriptors look like Table 112.
238
Offset
Offset
Offset
0Ch
0Ch
0Ch
00h
04h
08h
00h
04h
08h
00h
04h
08h
Offset
00h
02h
04h
06h
OWN
OWN
OWN
31
31
31
OWN
15
30
30
30
ADD_
ADD_
ADD_
FCS
FCS
FCS
29
14
29
29
LTINT
LTINT
LTINT
ADD_
28
FCS
28
28
13
P R E L I M I N A R Y
27-26
27
27
LTINT
12
Am79C976
STP
25
26
26
USER SPACE
USER SPACE
USER SPACE
TBADR[31:0]
TBADR[31:0]
TBADR[31:0]
11
Reserved
Reserved
TBADR[15:0]
When SWSTYLE is set to 4, then the software struc-
tures are defined to be 32 bits wide, and transmit de-
scriptors look like Table 113.
When SWSTYLE is set to 5, then the software struc-
tures are defined to be 32 bits wide, and transmit de-
scriptors look like Table 114. Also when SWSTYLE is
5, the Am79C976 controller uses 64-bit addressing for
software structures that are located above the 32-bit
address boundary.
ENP
STP
STP
Reserved
24
25
25
BCNT
10
ENP
ENP
23
24
24
KILL
22
23
23
STP
9
21-18
22-16
22-16
ENP
8
TCC[1:0]
17-16
15-12
TBADR[23:16]
BCNT
BCNT
11-4
15-0
TCI[15:0]
7-0
BCNT
15-0
8/01/00
3-0