AM79C976 Advanced Micro Devices, AM79C976 Datasheet - Page 171

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

Offset 1B2h
XMT_RING_LEN: Transmit Ring Length Register
Offset 140h
Offset 188h
8/01/00
15-0
15-0
Bit
Bit
XMT_RING_
Name
Name
LEN
VID
Vendor ID. The PCI Vendor ID register is a 16-bit register that identifies the manufacturer of the
Am79C976 controller. AMD’s Vendor ID is 1022h. Note that this Vendor ID is not the same as the
Manufacturer ID in CSR88 and CSR89. The Vendor ID is assigned by the PCI Special Interest
Group.
The Vendor ID is not normally programmable, but the Am79C976 controller allows this due to
legacy operating systems that do not look at the PCI Subsystem Vendor ID and the Vendor ID to
uniquely identify the add-in board or subsystem that the Am79C976 controller is used in.
Note: If the operating system or the network operating system supports PCI Subsystem
Vendor ID and Subsystem ID, use those to identify the add-in board or subsystem and
program the VID with the default value of 1022h.
Software supplied by AMD may not operate if the VID is anything other than 1022h.
This register is an alias of the PCI configuration space Vendor ID field at offset 00h and of BCR35.
Transmit Ring Length. Contains the two's complement of the transmit descriptor ring length. This
register is initialized during the optional Am79C976 controller initialization routine based on the
value in the TLEN field of the initialization block. However, this register can be manually altered.
The actual transmit ring length is defined by the current value in this register. The ring length can
be defined as any value from 1 to 65535.
This register is an alias of CSR78.
Table 83.
Table 82. VID_A: PCI Vendor ID Alias Register
XMT_RING_LEN: Transmit Ring Length Register
P R E L I M I N A R Y
Am79C976
This register is a writable alias of the Vendor ID field at
offset 0 in PCI configuration space, which is read only.
The purpose of this register is to allow the PCI Vendor
ID value to be loaded from the serial EEPROM.
The contents of this register are set to 1022h when the
RST pin is asserted, before the serial EEPROM is
read, and after a serial EEPROM read error.
The contents of this register are set to the default value
0 when the RST pin is asserted. This register is not af-
fected by the serial EEPROM read operation or by a se-
rial EEPROM read error.
The contents of this register are cleared to 0 when the
RST pin is asserted, before the serial EEPROM is
read, and after a serial EEPROM read error.
Description
Description
171