Mercedes-Benz D2B User manual

03-09-04
416 HO D2B (CooksonI)
Domestic Digital Bus
(D2B)

2
These technical training materials are current as of the date noted on the materials, and may be revised or updated without notice.
Always check for revised or updated information.
To help avoid personal injury to you or others, and to avoid damage to the vehicle on which you are working, you must always refer
to the latest Mercedes-Benz Technical Publication and follow all pertinent instructions when testing, diagnosing or making repair.
Illustrations and descriptions in this training reference are based on preliminary information and may not correspond to the final US
version vehicles. Refer to the official introduction manual and WIS when available.
Copyright Mercedes-Benz USA, LLC, 2004
WIS document numbers shown apply to WIS Version USA/CDN at dateof writing.
Reproduction by any means or by any information storage and retrieval system or translation in whole or part is not permitted
without written authorization from Mercedes-Benz USA, LLC or it's successors.
Published by Mercedes-Benz USA, LLC
Printed in U. S.A.

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•D2B acronym is derived from “Domestic Digital Bus”
•D2B utilizes fiber optics to transmit data and control signals in the form
of light -an optical network
•D2B components convert electrical signals into light signals or pulses
•Light pulses are sent to next component using a fiber optic transceiver (FOT)
•Each component uses 2 FOT’s-FOT ‘out’and FOT ‘in’
•Receiving D2B component converts optical data back into electrical
signals and either uses the information to operate or passes the data on
to the next component
What is D2B?
FOT out FOT in
Component 1 Component 2
Fiber optic cable

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Component
Component Component Component
Component
Component
D2B components are connected by:
•an optical ring
Fiber optic cable between each D2B
component, connects components in
series
&
•electrical wake-up lines
Single wire from each component is
connected together using connector
block or soldered ‘Z’splice –star
topology
Basic Arrangement
Z splice
or connector

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ƒTransmission Medium (Core)
Function: Carry optical signal
Diameter: 1.0 mm
‚Reflective Cladding
Function: Contain light within core
•Protective Jacket
Function: Protect cladding and core
Diameter: 2.2 mm
Color: Orange
D2B Fiber Optic Cable
ƒ
•
‚
Advantages:
•Impervious to electromagnetic interference
•Lighter than wire
•Improved signal quality
•Fewer electrical connections
•Easily configured
•5.6 MB/sec data transfer
(~ 11 times faster than CAN C)
Disadvantages:
•Fragile
•Repairs not possible without special
equipment

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Light passage
through a slightly
bent fiber
•Light passage through a straight
fiber:
Handle With Care!
•Repairs to fiber optic cables
not feasible as it requires
special tools to ensure a
perfect fit
Light passage
through a stressed
fiber

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Fiber Optic Cable Layout
Connection Configuration
Max. cable lengths -0 couplers = 10m / 1 coupler = 7m / 2 couplers = 3.6m
•Optical cables have one end clear
and the other end red
•Light is transmitted into the clear end
•Always ensure that ring follows
a red-to-clear, clear-to-red logic
•Ensure that red end is always on
the chamfered side of the connector
•In-Line couplers follow the same
logic as other ring connectors
Coupler part # 000 545 33 84

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Ring Master
•Ring master of the D2B system is either the
Radio, COMAND or MCS.
•Ring master is responsible for:
•Storing the ring configuration
•Providing voltage for the wake-up lines
•Issuing an electrical wake-up signal
•Issuing a ‘ring start’optical message
•Maintaining ‘ring lock’after ‘ring start’
•Switching off the ring
•Determining & storing fault codes
related to itself and ring errors
•Diagnostic gateway between CAN B
and D2B components
•Gateway between D2B components &
CAN B
•Performing a diagnostic wake-up upon
request from SDS / DAS
Radio
COMAND
MCS

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Electrical Wake-Up Line
•Fiber Optic Transceiver's
(FOT’s) draw a large
amount of current & need to
be put to sleep whenever
ring is not being used
•Wake-up line is always
supplied battery voltage
from D2B master
•To wake up components, a
wake-up signal is sent on
wake-up line from D2B
Master
•Wake-up line is also
used to assist diagnosis
when master is instructed to
by SDS / DAS
Optical
Electrical
or MCS
Shown with optional equipment

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Electrical Wake-Up Wiring
•Wake-up lines are Z spliced
on all models except:
-203 / 209 / 230 / 463
(which use a X30/8 connector)
•X30/8 connector block
connects all wake-up lines.
Location: 203 / 209 = right front sill trough 230 = behind driver seat under carpet
463 = behind dash left side near hood release
Z splice X30/8 connector block
Bridge cover pulled
up into ‘test position’
disconnecting
wake-up lines
Bridge cover removed
showing bridge contacts
Bridge cover removedX30/8