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Technical Bulletin on the Artisoft AE-3 Ethernet card

LANtastic for ARTISOFT

Artisoft Technical Bulletin  <see note at bottom>

TITLE:           AE-3 Ethernet Adapter Low-Level Information
UPDATED:         04.30.95
CLASSIFICATION:  Network interface card

The Artisoft AE-3 Ethernet Adapter, uses the National Semiconductor 
83902 Network Interface Controller (ST-NIC).  This document assumes the 
reader has access to the National Semiconductor Data Communications LAN 
Handbook.  This book contains information on the 83902 chipset, 
application notes and 802.3 specifications.

NIC Registers
The 8 bit 8390 internal registers are mapped into PC I/O space.  The base
address is jumper selectable on the AE-3 card.  The I/O bases 300h, 320h, 
340h or 360h are available.  The base address is the address where the NIC
command register will be mapped into PC I/O space.  The AE-3 will decode a
block of 32 I/O ports, starting at the selected base address.  The first 16
ports will be the NIC internal registers.  For example, if you select an 
I/O base of 320h, the NIC command register will be at 320h and the NIC ISR 
(Interrupt Status Register) will be at I/O base + 7h or 327h.

Data Port
All data to and from the network must pass through the data port.  The data
port is located at I/O base + 10h.  The data port is controlled by the NIC
Remote DMA.  All read/writes to the data port cause a remote DMA cycle in 
the NIC.  If the NIC is in 8 bit mode, the data port is an 8 bit port.  If
the NIC is in 16 bit mode, the data port is 16 bits wide.  Always make sure
to use the proper size instruction when transferring data to or from the 
AE-3.  For example, if you are running in 16 bit mode, use INSW rather than
the INSB to string-move the data.  Always take care to insure that the NIC
Remote DMA count is the same as the number of bytes you will be moving.  If
the NIC Remote DMA count reaches 0 and the driver issues another in/out 
instruction, the AE-3 will lock up the host PC by deasserting IOCHREADY.

NIC Reset
A complete reset of the NIC is performed by writing a byte to I/O base + 
17h.  It is recommended that you issue a reset before performing any action
on the NIC.

Onboard RAM
The onboard RAM is mapped into NIC address space as follows:

                        8K RAMs           32K RAMs 
8  bit mode             40h - 5Fh         01h - 7Fh
16 bit mode             40h - 7Fh         01h - FEh

Notes:  The NIC addresses are given in NIC page format.  If Novell 
emulation mode is selected (W10), 32K RAMs will appear as 8K RAMs.

Ethernet IEEE 802.3 Address
The unique 6 byte Ethernet Address of each AE-3 is contained in an onboard 
PROM.  The PROM is mapped into NIC address space at page 00.  Always use 8 
bit mode on the NIC to read this PROM.  The format of the PROM is as 

A0 A0 A1 A1 A2 A2 A3 A3 A4 A4 A5 A5 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 MM MM MM MM

The IEEE Ethernet address is contained in A0 through A5.  The mode byte 
(MM) is for determining if the AE-3 is in an 8 bit or a 16 bit slot.  If 
MM = 57h (ASCII "W"), the AE-3 is in a 16 bit (word) slot.  If MM = 42h 
(ASCII "B"), the AE-3 is in an 8 bit (byte) slot, or the 8 bit override
jumper (W9) is selected.

DMA Operation
Direct Memory Access (DMA) can be used to transfer data on and off the AE-3
adapter instead of the data port.  Onboard jumpers allow selection of 8 bit 
DMA channels 1 and 3 or 16 bit channels 5 and 7.

ARTISOFT, Inc. makes no warranties as to the completeness or accuracy of this
document.  LANtastic is a trademark of ARTISOFT, Inc.  Brand names, company 
names, and product names are trademarks or registered trademarks of their 
respective companies.

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