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Attachment Unit Interface (AUI) Circuitry
The Attachment Unit Interface (AUI) is the interface between the LANIC board
and the Medium Attachment Unit (MAU). The
AUt
MA U, and the coaxial
trunk cable comprise an analog network. The analog network provides the
physical connection between Local Area Network (LAN) nodes.
A block diagram of the AUf interface circuitry is shown in Figure
3-2.
The AUI
interface consists of four blocks:
• A type
802.3
chip
• Level 1 circuitry
• MAU power control
• AVI activity trace LEDs
TO PROTOCOL
CONTROLLER
~--...,.-~
SWITCHED 12 VOLT
t----~)-~
Figure 3-2. AUf Interface Block Diagram
The
8023
chip performs the following functions:
Decodes receive clock
Decodes receive data
Generates transmit clock
Encodes transmit data with clock
Decodes CONTROL IN
Detects carrier present
Loops transmit data to receive data for diagnostics
The AUI side of the
8023
chip consists of two balanced receivers
(DATA5IN
+
CONTROL5IN) and one balanced driver (DATA50UT). The
signals from these circuits are put through a passive balancing network and are
then transformer coupled to the AUI pairs.
Principles of Operat.ion
3-14
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