AM79C970 Просмотр технического описания (PDF) - Advanced Micro Devices

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AM79C970

PCnet™-PCI Single-Chip Ethernet Controller for PCI Local Bus

Advanced Micro Devices 

PRELIMINARY

AMD

BASIC FUNCTIONS

System Bus Interface Function

The PCnet-PCI controller is designed to operate as a

Bus Master during normal operations. Some slave I/O

accesses to the PCnet-PCI controller are required in

normal operations as well. Initialization of the PCnet-

PCI controller is achieved through a combination of PCI

Configuration Space accesses, Bus Slave accesses,

Bus Master accesses and an optional read of a serial

EEPROM that is performed by the PCnet-PCI control-

ler. The EEPROM read operation is performed through

the Microwire interface. The ISO 8802-3 (IEEE/ANSI

802.3) Ethernet Address may reside within the serial

EEPROM. Some PCnet-PCI controller configuration

registers may also be programmed by the EEPROM

read operation.

The APROM, on-chip board-configuration registers,

and the Ethernet controller registers occupy 32-bytes of

I/O space which can be located on a wide variety of

starting addresses by modifying the Base Address Reg-

ister in the PCI Configuration Space.

space that must begin on a 32-byte block boundary. The

I/O base address can be changed to any 32-bit quantity

that begins on a 32-bit block boundary by modifying the

Base Address Register in the PCI Configuration Space.

The 32-byte I/O space is used by the software to pro-

gram the PCnet-PCI controller operating mode, to en-

able and disable various features, to monitor operating

status and to request particular functions to be executed

by the PCnet-PCI controller.

The third portion of the software interface is the descrip-

tor and buffer areas that are shared between the soft-

ware and the PCnet-PCI controller during normal

network operations. The descriptor area boundaries are

set by the software and do not change during normal

network operations. There is one descriptor area for re-

ceive activity and there is a separate area for transmit

activity. The descriptor space contains relocatable

pointers to the network packet data and it is used to

transfer packet status from the PCnet-PCI controller to

the software. The buffer areas are locations that hold

packet data for transmission or that accept packet data

that has been received.

Software Interface

The software interface to the PCnet-PCI controller is di-

vided into three parts. One part is the PCI configuration

registers. They are used to identify the PCnet-PCI con-

troller, and are also used to setup the configuration of

the device. The setup information includes the I/O base

address and the routing of the PCnet-PCI controller in-

terrupt channel. This allows for a jumperless

implementation.

The second portion of the software interface is the direct

access to the I/O resources of the PCnet-PCI controller.

The PCnet-PCI controller occupies 32-bytes of I/O

Network Interfaces

The PCnet-PCI controller can be connected to an 802.3

network via one of two network interfaces. The Attach-

ment Unit Interface (AUI) provides an ISO 8802-3

(IEEE/ANSI 802.3) compliant differential interface to a

remote MAU or an on-board transceiver. The

10BASE-T interface provides a twisted-pair Ethernet

port. While in auto-selection mode, the interface in use

is determined by an auto-sensing mechanism which

checks the link status on the 10BASE-T port. If there is

no active link status, then the device assumes an AUI

connection.

Am79C970

1-887

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