am79c961 Advanced Micro Devices, am79c961 Datasheet - Page 34

• Manufacturer Part Number: am79c961
• Description: Pcnettm-isa Jumperless Single-chip Ethernet Controller For Isa
• Manufacturer: Advanced Micro Devices

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 configu-
ration space is defined as a set of 8 bit registers. These
registers are used by the Plug and Play software con-
figuration to issue commands, access the resource
information, check status, and configure the PCnet-ISA
controller hardware.
The address and Write_DATA ports are located at fixed,
predefined I/O addresses. The Write_Data port is lo-
cated at an alias of the Address port.
auto-configuration ports use a 12-bit ISA address
decode.
The READ_DATA port is relocatable within the range
0x203–0x3FF
WRITE_DATA port.
ADDRESS PORT
The internal Plug and Play registers are accessed by
writing the address to the ADDRESS PORT and then
1-508
ADDRESS
WRITE-DATA
READ-DATA
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 compatability with other ISA
bus adapters
Name
AMD
Port
0X279 (Printer Status Port)
0xA79 (Printer status port
+ 0x0800)
Relocatable in range
0x0203-0x03FF
by
a
Location
command
written
Write-only
Write-only
Read-only
P R E L I M I N A R Y
All three
Type
to
Am79C961
the
+
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 Register
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
erating in Plug and Play mode. It will not respond to any
memory or I/O accesses, nor will the PCnet-ISA
troller drive any interrupts or DMA channels.
The initiation key places the PCnet-ISA
configuration mode. This is done by writing a predefined
pattern to the ADDRESS PORT. If the proper sequence
of I/O writes are detected by the PCnet-ISA
Plug and Play auto-configuration ports are enabled.
This sequence must be sequential, i.e., any other I/O ac-
cess to this I/O port will reset the state machine which is
checking the pattern. Interrupts should be disabled dur-
ing this time to eliminate any extraneous I/O cycles.
The exact sequence for the initiation key is listed below
in hexadecimal.
Isolation Protocol
A simple algorithm is used to isolate each Plug and Play
card. This algorithm uses the signals on the ISA bus and
requires lock-step operation between the Plug and Play
hardware and the isolation software.
6A, B5, DA, ED, F6, FB, 7D, BE
DF, 6F, 37, 1B, 0D, 86, C3, 61
B0, 58, 2C, 16, 8B, 45, A2, D1
E8, 74, 3A, 9D, CE, E7, 73, 39
+
controller is disabled at reset when op-
+
device into the
+
device, the
+
con-