AM79C961AVC datasheet(49/206 Pages) AMD

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Am79C961A

PLUG AND PLAY

Plug and Play is a standardized method of configuring

jumperless adapter cards in a system. Plug and Play is

a Microsoft standard and is based on a central software

configuration program, either in the operating system

or elsewhere, which is responsible for configuring all

Plug and Play cards in a system. Plug and Play is fully

supported by the PCnet-ISA II ethernet controller.

For a copy of the Microsoft Plug and Play specification

contact Microsoft Inc. This specification should be

referenced in addition to PCnet-ISA II Technical

Reference Manual and this data sheet.

Operation

If the PCnet-ISA II ethernet controller is used to boot off

the network, the device will come up active at RESET,

otherwise it will come up inactive. Information stored in

the serial EEPROM is used to identify the card and to

describe the system resources required by the card,

such as I/O space, Memory space, IRQs and DMA

channels. This information is stored in a standardized

Read Only format. Operation of the Plug and Play

system is shown as follows:

s Isolate the Plug and Play card

s Read the cards resource data

s Identify the card

s Configure its resources

The Plug and Play mode of operation allows the follow-

ing benefits to the end user.

s Eliminates all jumpers or dip switches from the

adapter card

s Ease of use is greatly enhanced

s Allows the ability to uniquely address identical cards

in a system, without conflict

s Allows the software configuration program or OS to

read out the system resource requirements

required by the card

s Defines a mechanism to set or modify the current

configuration of each card

s Maintain backward compatibility with other ISA bus

adapters

Auto-Configuration Ports

Three 8 bit I/O ports are used by the Plug and Play con-

figuration software on each Plug and Play device to

communicate with the Plug and Play registers. The

ports are listed in the table below. The software config-

uration space is defined as a set of 8 bit registers.

These registers are used by the Plug and Play software

configuration to issue commands, access the resource

information, check status, and configure the PCnet-ISA

II controller hardware.

The address and Write_DATA ports are located at

fixed, predefined I/O addresses. The Write_Data port is

located at an alias of the Address port. All three

auto-configuration ports use a 12-bit ISA address

decode.

The READ_DATA port is relocatable within the range

0x 2 0 3 – 0x 3 F F b y a c o m m a nd wr i tte n to th e

WRITE_DATA port.

ADDRESS PORT

The internal Plug and Play registers are accessed by

writing the address to the ADDRESS PORT and then

either reading the READ_DATA PORT or writing to the

WRITE_DATA PORT. Once the ADDRESS PORT has

been written, any number of reads or writes can occur

without having to rewrite the ADDRESS PORT.

The ADDRESS PORT is also the address to which the

initiation key is written to, which is described later.

WRITE_DATA PORT

The WRITE_DATA PORT is the address to which all

writes to the internal Plug and Play registers occur. The

destination of the data written to the WRITE_DATA

PORT is determined by the last value written to the

ADDRESS PORT.

READ_DATA PORT

The READ_DATA PORT is used to read information

from the internal Plug and Play registers. The register

to be read is determined by the last value of the

ADDRESS PORT.

The I/O address of the READ_DATA PORT is set by

writing the chosen I/O location to Plug and Play Reg-

ister 0. The isolation protocol can determine that the

address chosen is free from conflict with other devices

I/O ports.

Initiation Key

The PCnet-ISA II controller is disabled at reset when

operating in Plug and Play mode. It will not respond to

any memory or I/O accesses, nor will the PCnet-ISA II

controller drive any interrupts or DMA channels.

The initiation key places the PCnet-ISA II device into

the configuration mode. This is done by writing a pre-

defined pattern to the ADDRESS PORT. If the proper

sequence of I/O writes are detected by the PCnet-ISA

II device, the Plug and Play auto-configuration ports

Port Name

Location

Type

ADDRESS

0X279 (Printer Status Port)

Write-only

WRITE-DATA

0xA79 (Printer status port +

0x0800)

Write-only

READ-DATA

Relocatable in range

0x0203-0x03FF

Read-only

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