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.

3
•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

4
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

5
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

6
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

7
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

8
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

9
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

10
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

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•Master issues wake-up pulse by pulling
wake-up line low for ~ 80 ms
Electrical Wake-up
0
12
ms
v
80 ms approx.
5
3
High
Low
Undefined
Ring Start
•Components recognize this duration as
a wake-up pulse and wake-up
•Master issues a optical pulse (ring
start optical command) or MCS
•Optical pulse transmits around the
ring and back to the master. Master
now sends constant optical signal -
‘ring lock’
Tip: CD changer (if installed) can be heard
examining the CD magazine if ring lock
occurs.

12
Ring Failure
Version Coding & Configuration
Signal Phasing
Electrical fault
Optical fault
Attenuation

13
•In order for the ring to function properly, the master MUST know the
number of components on the ring and ORDER of those components
with respect to the master.
•Refer to the latest Service Information or bulletin for the correct
configuration:
Currently: Date: August 2000 & October 2002
Document No.: SI-82.64/135 & S-B-82.70/135B
Group: 82
NOTE: Improper version coding and / or incorrect sequencing of
components may result in intermittent and / or abnormal
operation of the ring.
Always check ring configuration is correct and
corresponds to equipment level using SDS / DAS.
Version Coding & Configuration

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Configuration
Name -order in ring
Specified value -component list configured by using SDS / DAS
Actual value -what the master ‘see’son ring start

15
What is Signal Phasing?
•To set or regulate so as to be synchronized
•Out of phase = Operating in an unsynchronized way
•In D2B, Signal Phasing is the process of sending and receiving data
according to a prescribed time table
•D2B “Master”knows when it sent data and when it should receive
that data back
e.g. Time it takes:
Ødata to reach 1st component
+
Øcomponent to respond to data and send data on
+
Ødata to reach next component ….etc

16
MCS
Fiber Optic Transceiver
Slave
(Bose Amp)
Slave
(TELE AID)
Slave
(CD Changer)
4 bit signal is sent
(timer begins)
D2B Signal Phasing Error
½bit of data is lost
Each component
receives, processes
and resends the 4
bit signal within a
specified time range
(e.g. 1 -5 ms)
·
·
·
Time slot reserved
for receiving the 4
bit signal.
This could be due to:
-tolerances within several ring components
-excessive lengths of fiber optic cable added into the ring

17
Electrical Wake-up
0
12
ms
v
5
3
Ring Start (with open at TELE AID)
Open
•Master issues electrical wake-up pulse
•Components wake-up except for
TELE AID
•Master does not receive optical pulse
back because TELE AID cannot
wake-up
•3 additional wake-up pulses are sent
•With each wake-up pulse a optical
pulse was also issued
or MCS
Zzzzzz….
Tip: D2B components may be heard clicking
during this process indicating that they
are electrically awake.

18
Ring Start (with open at TELE AID)
Open
•After the 4th attempt with no
ring lock established, all D2B
components that are awake
send a ‘roll call’pulse back to
the master
•In this case only 2 ‘roll call’
pulses were received by the
master
-this information is used
to determine fault
location
•Ring lock cannot be
established
•No further attempts are made
to start ring (components go
back to sleep), unless the
system is switched on again
or MCS
Zzzzzz….

19
Determining Fault Location
or MCS
•‘Roll call’messages that
returned to master, indicate
number of components able to
communicate with master on
the optical ring
•Appropriate fault code stored
e.g. N1111 no data transferred
between D2B master and a D2B
component possible: The
component at location _ reports a
fault in the ring.
•Location (or position) number
indicates number of
components master heard back
from, counting around the ring
backwards
Open
Location 1Location 1
Location 2Location 2
Location 3Location 3
Location 4Location 4
Location 5Location 5

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Electrical or Optical Fault?
•Fault code does not indicate what the fault is, only the location that was
last heard from.
e.g. N1111 no data transferred between D2B master and a D2B component possible:
The component at location _ reports a fault in the ring.
•To determine if the fault is electrical or optical we can perform a ‘test of
the wake-up line to all components’using the SDS / DAS. This is
sometimes referred to as a diagnostic wake-up.
•When prompted, Master will issue an extended wake-up signal that the
D2B components will respond to
•D2B components on the ring will each respond by pulling the wake-up
line low at specific time intervals
•Master will monitor wake-up line and via SDS / DAS display results of
the test