AM79C971VCW Advanced Micro Devices, AM79C971VCW Datasheet - Page 186

• Manufacturer Part Number: AM79C971VCW
• Description: PCnet-FAST Single-Chip Full-Duplex 10/100 Mbps Ethernet Controller for PCI Local Bus
• Manufacturer: Advanced Micro Devices

RMD3
Bit
31-0
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 49 (CXDA = Current
Transmit Descriptor Address).
When SWSTYLE (BCR 20, bits 7-0) is set to 2, the soft-
ware structures are defined to be 32 bits wide, and
transmit descriptors look like Table 50 (CXDA = Current
Transmit Descriptor Address).
186
CXDA+0Ch
CXDA+0Ch
CXDA+00h
CXDA+04h
CXDA+08h BUFF UFLO
CXDA+00h BUFF UFLO
CXDA+04h
CXDA+08h
Address
Address
CXDA+00h
CXDA+02h
CXDA+04h
CXDA+06h
Address
US
Name
OWN
OWN
31
31
BUFF
OWN
15
1
User Space. Reserved for user
defined space.
ERR
ERR
Description
30
30
UFLO
ADD_
ADD_
ERR
FCS
DEF
DEF
FCS
14
EX
EX
29
29
1
Table 49. Transmit Descriptor (SWSTYLE = 0)
Table 50. Transmit Descriptor (SWSTYLE = 2)
Table 51. Transmit Descriptor (SWSTYLE = 3)
MORE/
MORE/
LTINT
LTINT
LCOL
LCOL
ADD_
FCS
DEF
28
28
EX
13
1
P R E L I M I N A R Y
LCAR
LCAR
ONE
ONE
27
27
MORE/
LTINT
LCOL
12
1
Am79C971
RTRY
RTRY
DEF
DEF
26
26
LCAR
USER SPACE
USER SPACE
ONE
TBADR[31:0]
TBADR[31:0]
11
TBADR[15:0]
When SWSTYLE (BCR 20, bits 7-0) is set to 3, then the
software structures are defined to be 32 bits wide, and
transmit descriptors look like Table 51 (CXDA = Current
Transmit Descriptor Address).
TMD0
Bit
31-0
RES
STP
STP
25
25
RTRY
DEF
Name
TBADR
10
ENP
RES
ENP
24
24
BPE
RES
BPE
RES
23
23
STP
9
Transmit Buffer address. This
field contains the address of the
transmit buffer that is associated
with this descriptor.
Description
BCNT
22-16
22-16
RES
RES
RES
ENP
8
15-12
15-12
1111
1111
RES
TDR
TBADR[23:16]
11-4
RES
11-4
RES
7-0
BCNT
BCNT
TRC
TRC
3-0
3-0