AM79C978 Advanced Micro Devices, AM79C978 Datasheet - Page 200

• Manufacturer Part Number: AM79C978
• Description: Single-Chip 1/10 Mbps PCI Home Networking 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 82 (CRDA = Current
Receive Descriptor Address).
When SWSTYLE (BCR 20, bits 7-0) is set to 2, then the
software structures are defined to be 32 bits wide, and
200
CRDA+0Ch
CRDA+0Ch
CRDA+00h
CRDA+04h OWN ERR
CRDA+08h RES
CRDA+00h
CRDA+04h
CRDA+08h
Address
Address
CRDA+00h
CRDA+02h
CRDA+04h
CRDA+06h
Address
OWN
31
31
OWN
15
30
1
0
ERR
30
47
Match = 1 Packet Accepted
Match = 0 Packet Rejected
Received Message
Destination Address
FRA
29
M
ERR
FRAM
14
1
0
29
OFL
Table 83. Receive Descriptor (SWSTYLE = 2)
28
Table 82. Receive Descriptor (SWSTYLE = 0)
Table 84. Receive Descriptor (SWSTYLE = 3)
O
FRAM
OFLO
CRC
1
27
13
28
Figure 51. Address Match Logic
1
0
1
0
RES
BUF
26
F
CRC
OFLO
27
12
USER SPACE
1
0
STP ENP BPE
CRC
GEN
25
SEL
Am79C978
RFRTAG[14:0]
BUFF
26
CRC
USER SPACE
RBADR[31:0]
24
RBADR[31:0]
11
RBADR[15:0]
receive descriptors look like Table 83 (CRDA = Current
Receive Descriptor Address).
When SWSTYLE (BCR 20, bits 7-0) is set to 3, then the
software structures are defined to be 32 bits wide, and
receive descriptors look like Table 84 (CRDA = Current
Receive Descriptor Address).
STP
25
23
31
32-Bit Resultant CRC
BUFF
10
26
64
PAM
22
ENP
6
24
63
STP
LAFM
MUX
Address Filter
9
21
RES
BPE
(LADRF)
23
Logical
MCNT
0
BCNT
BAM
ENP
20
22-16
8
RES
RES
0
Match
19-16
RES
RBADR[23:16]
15-12
0000
1111
15-12
0000
1111
7-0
22206B-54
MCNT
BCNT
MCNT
BCNT
11-0
11-0