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Introduction - Motorola MC68838 User Manual

Media access controller
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SECTION 1

INTRODUCTION

The MC68838 media access controller (MAC) chip implements the MAC protocol for a
station operating under the ANSI standard for FDDI LANs (see Figure 1-1). FDDI is a
125-Mbit/sec, fiber-optic-based token ring designed to accommodate rings up to 1000
stations, 2 km between stations, and 200-km total ring length.
USER SYSTEM BUS
PIN
FROM FIBER-OPTIC CABLE
The ANSI standard specifies the data link MAC layer, the physical and physical-media-
dependent entities, and the station management and submanagement physical
connection management.
The MAC protocol, the lower sublayer of the data link layer, provides for fair and
deterministic sharing of the physical medium, address recognition, FCS generation and
verification, frame insertion, frame repetition, frame removal, token generation, and
certain error recovery procedures.
MOTOROLA
HOST PROCESSOR
FSI - MC68839
MAC - MC68838
ELM - MC68837
AMPLIFIER
FCG - MC68836
Figure 1-1. Motorola FDDI Architecture
MC68838 USER'S MANUAL
SHARED MEMORY
USER SYSTEM
PAL
CAM INTERFACE
OPTIONAL
EXTERNAL CAM
DRIVER
TO FIBER-OPTIC CABLE
LED
1-1

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