am79c961a Advanced Micro Devices, am79c961a Datasheet - Page 49

• Manufacturer Part Number: am79c961a
• Description: Pcnet?-isa Ii Jumperless, Full Duplex Single-chip Ethernet Controller For Isa
• Manufacturer: Advanced Micro Devices

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:
The Plug and Play mode of operation allows the follow-
ing benefits to the end user.
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.
Isolate the Plug and Play card
Read the cards resource data
Identify the card
Configure its resources
Eliminates all jumpers or dip switches from the
adapter card
Ease of use is greatly enhanced
Allows the ability to uniquely address identical cards
in a system, without conflict
Allows the software configuration program or OS to
read out the system resource requirements
required by the card
Defines a mechanism to set or modify the current
configuration of each card
Maintain backward compatibility with other ISA bus
adapters
Am79C961A
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
0 x 2 0 3 – 0 x 3 F F by a c o m m a n d w r i t t e n t o t h 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
WRITE-DATA
READ-DATA
Port Name
ADDRESS
0X279 (Printer Status Port)
0xA79 (Printer status port +
0x0800)
Relocatable in range
0x0203-0x03FF
Location
Read-only
Write-only
Write-only
Type
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