AM79C976 datasheet(171/309 Pages) AMD

171 / 309 page

8/01/00

Am79C976

171

P R E L I M INARY

9,'B$ 3&,9HQGRU,'$OLDV5HJLVWHU

Offset 1B2h

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.

Table 82. VID_A: PCI Vendor ID Alias Register

XMT_RING_LEN: Transmit Ring Length Register

Offset 140h

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.

Table 83. XMT_RING_LEN: Transmit Ring Length Register

;0732//7,0( 7UDQVPLW3ROO 7LPHU 5HJLVWHU

Offset 188h

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.

Bit

Name

Description

15-0

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.

Bit

Name

Description

15-0

XMT_RING_

LEN

Transmit Ring Length. Contains the two's complement of the transmit descriptor ring length. This

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.

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