AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 227

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

Receive Descriptors
When SWSTYLE (BCR20, bits 7-0) is set to 0, then the
software structures are defined to be 16 bits wide, and
receive descriptors look like Table 100.
When SWSTYLE is set to 2, then the software struc-
tures are defined to be 32 bits wide, and receive de-
scriptors look like Table 101.
When SWSTYLE is set to 3, then the software struc-
tures are defined to be 32 bits wide, and receive de-
scriptors look like Table 102.
8/01/00
Offset
0Ch
00h
04h
08h
Offset
00h
02h
04h
06h
OWN ERR
RES
31
OWN
15
30
0
47
Match = 1 Packet Accepted
Match = 0 Packet Rejected
Received Message
Destination Address
FRA
29
M
ERR
14
0
OFL
28
O
FRAM
CRC
1
27
13
0
0
1
P R E L I M I N A R Y
26
OFLO
12
0
STP ENP
CRC
GEN
SEL
25
Am79C976
RFRTAG[14:0]
USER SPACE
RBADR[31:0]
CRC
24
11
RBADR[15:0]
When SWSTYLE is set to 4, then the software struc-
tures are defined to be 32 bits wide, and receive de-
scriptors look like Table 103.
When SWSTYLE is set to 5, then the software struc-
tures are defined to be 32 bits wide, and receive de-
scriptors look like Table 104. Also, when SWSTYLE is
5, the Am79C976 controller uses 64-bit addressing for
software structures that are located above the 32-bit
address boundary.
BCNT
31
23
32-Bit Resultant CRC
10
26
64
PAM
22
6
63
MUX
STP
LAFM
Address Filter
9
21
(LADRF)
Logical
0
MCNT
BAM
20
ENP
8
0
Match
19-16
RES
RBADR[23:16]
7-0
MCNT
BCNT
15-0
21485B55
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