AM79C971VCW Advanced Micro Devices, AM79C971VCW Datasheet - Page 172

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

7-0
BCR23: PCI Subsystem Vendor ID Register
Note: Bits 15-0 in this register are programmable
through the EEPROM.
Bit
31-16 RES
172
MIN_GNT
Name
Minimum Grant. Specifies the
minimum length of a burst period
the Am79C971 controller needs
to keep up with the network activ-
ity. The length of the burst period
is calculated assuming a clock
rate of 33 MHz. The register val-
ue specifies the time in units of 1/
4 s. MIN_GNT is aliased to the
PCI configuration space register
MIN_GNT (offset 3Eh). The host
will use the value in the register to
determine the setting of the
Am79C971 Latency Timer regis-
ter.
Reserved locations. Written as
zeros and read as undefined.
mended to program the value of
18H via EEPROM. MAX_LAT is
not affected by S_RESET or
STOP.
Read accessible always; write
accessible only when either the
STOP or the SPND bit is set.
MIN_GNT is set to the value of
06h by H_RESET which results
in a default minimum grant of
1.5 s, which is the time it takes
the Am79C971 controller to read/
write half of the FIFO. (16 DWord
transfers in burst mode with one
extra wait state per data phase
inserted by the target.) Note that
the default is only a typical value.
It also does not take into account
any descriptor accesses. It is rec-
ommended to program the value
of 18H via EEPROM. MIN_GNT
is not affected by S_RESET or
STOP.
Description
P R E L I M I N A R Y
Am79C971
15-0
BCR24: PCI Subsystem ID Register
Note: Bits 15-0 in this register are programmable
through the EEPROM.
Bit
31-16 RES
15-0
BCR25: SRAM Size Register
Bit
Note: Bits 7-0 in this register are programmable
through the EEPROM.
31-8
SVID
SID
RES
Name
Name
Subsystem Vendor ID. SVID is
used together with SID (BCR24,
bits 15-0) to uniquely identify the
add-in board or subsystem the
Am79C971 controller is used in.
Subsystem Vendor IDs can be
obtained from the PCI SIG. A val-
ue of 0 (the default) indicates that
the Am79C971 controller does
not support subsystem identifica-
tion. SVID is aliased to the PCI
configuration space register Sub-
system Vendor ID (offset 2Ch).
Read accessible always. SVID is
read only. Write operations are
ignored. SVID is cleared to 0 by
H_RESET and is not affected by
S_RESET or by setting the STOP
bit.
Reserved locations. Written as
zeros and read as undefined.
Subsystem ID. SID is used to-
gether with SVID (BCR23, bits
15-0) to uniquely identify the add-
in
Am79C971 controller is used in.
The value of SID is up to the sys-
tem vendor. A value of 0 (the de-
fault)
Am79C971 controller does not
support subsystem identification.
SID is aliased to the PCI configu-
ration space register Subsystem
ID (offset 2Eh).
Read accessible always. SID is
read only. Write operations are
ignored. SID is cleared to 0 by
H_RESET and is not affected by
S_RESET or by setting the STOP
bit.
Reserved locations. Written as
zeros and read as undefined.
Description
Description
board
indicates
or
subsystem
that
the
the