System components
GF54.21>W>0009H
Central gateway control unit (CGW), component description
29.6.11
MODEL 963, 964
W54.21
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1422
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11
Location
A2
Central gateway control unit (CGW)
The central gateway control unit (CGW) (A2) is located
in the electronics compartment on the passenger side.
Task
The central gateway control unit (CGW) (A2) forms the central
interface of the vehicle networking and is directly connected to
the following 5 high
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speed bus systems:
•
Vehicle CAN (CAN 1)
•
Interior CAN (CAN 2)
•
Frame CAN (CAN 3)
•
Telematics CAN (CAN 9)
•
Diagnostic CAN (CAN 10)
Routing data
The main task of the central gateway control unit (CGW) (A2) is to
route individual CAN messages between the connected CAN data
bus systems. In other words, e.g. it issues messages from the
interior CAN (CAN 2) to the frame CAN (CAN 3).
The central gateway control unit (CGW) (A2) only knows which
messages are being routed to which CAN system, and not which
control unit must receive the individual messages.
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Control unit monitoring
The
central gateway control unit (CGW) (A2) monitors all control
units for failure except itself and the components of the Electronic
Brake Control control unit (EBS).
In the process, it checks whether a control unit actively
participates in the bus traffic. If a control unit does not send a
message after a long period, it assumes failure and issues a
corresponding fault code. In addition, the failure is displayed on
the instrument cluster control unit (ICUC) (A1).
Network management
The central gateway control unit (CGW) (A2) is responsible for
selectively waking up and putting asleep the connected control
units. All control units are awakened if a message is sent to a bus
system.
Sleep is initiated only when all control units have signaled sleep
readiness. As a result, synchronization occurs at sleep time.
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Bus termination resistors
Bus termination resistors are used to avoid reflections that would
lead to the falsification of actual information. The characteristic
impedance of the electrical line is important for the bus
termination resistor.
Bus termination resistors are installed for the following data bus
systems in the central gateway control unit (CGW) (A2):
•
Frame CAN (CAN 3)
•
Telematics CAN (CAN 9)
•
Diagnostic CAN (CAN 10)
Virtual control units
Virtual control units are not equipped with their own housing.
They are integrated into the hardware and software of other
control units. However, they do appear as individual control units
in the Star Diagnosis.
The following control units are realized as virtual control units in
the central gateway control unit (CGW) (A2):
•
The central data memory (CDS) (A2 a1)
•
The communications interface control unit (COM) (A2 a2)
•
The maintenance system control unit (MS) (A2 a3)
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Introduction of engine OM 471 and exhaust aftertreatment
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09/2011
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101
– This printout will not be recorded by the update service. Status: 09 / 2011 –
