Service manual

Service Manual
Part 2 - Interface cards
Ethernet interface
Where an Ethernet interface is fitted, it is provided by
one of two different types of Ethernet expansion card,
identified as Ethernet I and Ethernet II. Both cards can
support either a Thick' or 'thin' (Cheapernet) Ethernet
interface.
Overview
Ethernet was developed by the Xerox Corporation in the
early 1970s and a specification made available in 1980.
This specification known as the 'Blue Book' was used as
the basis for the IEEE and ECMA standards. All new
equipment (including this product) is or should be
designed to the IEEE standard. This allows networking
with existing Ethernet equipment, at least at the physical
level.
An understanding of the basic architecture of the
Ethernet/IEEE 802.3 standard is assumed. The Intel
publication The LAN Components User's Manual is
particularly useful and contains a suitable introduction to
local area network standards. It is recommended that
you obtain a copy if you require a wider understanding,
as reference to it is made in this document.
Ethernet I expansion card
Basic operation and block diagram
Figure 2-1: Ethernet I expansion card block diagram is a
block diagram of the Ethernet/Cheapernet podule. The
main functional blocks are:
• the net controller: Intel 82586 (LANCE)
• the serial interface adaptor: Intel 82501 (SIA)
• transceiver: Intel 82502
• attachment unit interface (AUI) socket (D-type)
• isolation transformers and power supply
• bus buffers and transceivers
• the RAM buffer
• the RAM page register
• a PROM based 'extended' podule ID
• the control register
• the PAL based state machine.
Figure 2-1: Ethernet I expansion card block diagram
Part 2 - Interface cards Issue 2, June 1991 2-1