AM79C971VCW Advanced Micro Devices, AM79C971VCW Datasheet - Page 185

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

21
20
LAFM
BAM
to a match of the frame’s destina-
tion address with the content of
the physical address register.
PAM is valid only when ENP is
set. PAM is set by the Am79C971
controller and cleared by the
host.
Logical Address Filter Match is
set by the Am79C971 controller
when it accepts the received
frame based on the value in the
logical address filter register.
LAFM is valid only when ENP is
set.
Am79C971
cleared by the host.
Broadcast Address Match is set
by the Am79C971 controller
when it accepts the received
frame, because the frame’s desti-
nation address is of the type
’Broadcast.’ BAM is valid only
when ENP is set. BAM is set by
the Am79C971 controller and
cleared by the host.
This bit does not exist when the
Am79C971 controller is pro-
grammed to use 16-bit software
structures for the descriptor ring
entries (BCR20, bits 7-0, SW-
STYLE is cleared to 0).
Note that if DRCVBC (CSR15, bit
14) is cleared to 0, only BAM, but
not LAFM will be set when a
Broadcast frame is received,
even if the Logical Address Filter
is programmed in such a way that
a Broadcast frame would pass
the hash filter. If DRCVBC is set
to 1 and the Logical Address Fil-
ter is programmed in such a way
that a Broadcast frame would
pass the hash filter, LAFM will be
set on the reception of a Broad-
cast frame.
This bit does not exist when the
Am79C971 controller is pro-
grammed to use 16-bit software
structures for the descriptor ring
entries (BCR20, bits 7-0, SW-
STYLE is cleared to 0).
LAFM
is
controller
set
P R E L I M I N A R Y
by
and
the
Am79C971
19-16 RES
15-12 ONES
11-00 BCNT
RMD2
Bit
30-16 RFRTAG
15-12 ZEROS
11-0
MCNT
Name
ZERO
This bit does not exist when the
Am79C971 controller is pro-
grammed to use 16-bit software
structures for the descriptor ring
entries (BCR20, bits 7-0, SW-
STYLE is cleared to 0).
Reserved locations. These loca-
tions should be read and written
as zeros.
These four bits must be written as
ones. They are written by the host
and
Am79C971 controller.
Buffer Byte Count is the length of
the buffer pointed to by this de-
scriptor, expressed as the two’s
complement of the length of the
buffer. This field is written by the
host and unchanged by the
Am79C971 controller.
This
Am79C971 controller will write a
zero to this location.
Receive Frame Tag. Indicates
the Receive Frame Tag applied
from the EADI interface. This field
is user defined and has a default
value of all zeros. When RX-
FRTG (CSR7, bit 14) is set to 0,
RFRTAG will be read as all zeros.
See the section on Receive
Frame Tagging for details.
This field is reserved. Am79C971
controller will write zeros to these
locations.
Message Byte Count is the length
in bytes of the received message,
expressed as an unsigned binary
integer. MCNT is valid only when
ERR is clear and ENP is set.
MCNT
Am79C971
cleared by the host.
Note: This is a 13-bit internal
counter.
Description
field
unchanged
is
is
written
controller
reserved.
by
by
185
The
and
the
the