Networking/Data Communication
Networking/data communication
Electronic networking in the 911 Carrera allows data and electrical information to be exchanged between various control units throughout the vehicle. This is realised with the aid of the internal high-speed network, the so-called CAN-BUS (Controller Area Network), and the fibre-optic network, the so-called MOST-BUS (Media Oriented System Transport).
In the 911 Carrera, up to 29 control units can be exchanging up to 2 MB of data per minute via the CAN bus at any time. Approx. 2,500 different signals have been defined to this end. Networking reduces the number of connections required so that the total length of cabling required can be kept significantly shorter.
Most of the network connections can be found in the following areas:
- In the area of engine management for high-speed information exchange.
- In the area of coordination of networked control engineering. Thus a PSM braking operation, for example, involves the control units for the brakes (PSM), engine, tyre pressure monitoring system and Tiptronic S.
- In the area of audio/communication for the joint transmission of digital audio and control data via the MOST-BUS.
- The use of network connections has enabled a reduction in weight of approx. 5 kg in the new 911 Carrera, even though functionality has been extended.
97 Basic topology of the data bus system in the 911 Carrera
The overview shows the networking of the control units:
97 Gateway controller
The gateway controller is actively involved with all CAN buses in the 911 Carrera. The gateway controller is a separate unit, rather than being integrated into the instrument cluster as on the Cayenne. It relays all messages and signals which are transmitted by control units for transmission via various buses. The transfer protocol of the gateway controller is defined in a so-called routing table. It also supports the test unit in diagnosing the vehicle by transmitting,
collecting and supplying numerous items of information on the vehicle.
The individual items of information concerned here are:
- Transmission of specified installation information on all bus systems
- Provision of actual installation information (CAN control units)
- Collection and provision of error bits for tester
- Acquisition and provision of information on control units which do not switch to sleep standby mode after terminal 15 "off"
- Acquisition and provision of general CAN bus information (e.g. single-wire operation, fault location info, etc.)
Parameterisation is carried out with the aid of the PIWIS tester.
The following operations and settings require to be carried out with the diagnostic tester when putting the gateway into operation in the vehicle:
- Check identification
- Encode specified installation
- Encode vehicle data (e.g. vehicle type etc.)
- Delete overflow counter (warning thresholds of an internal counter for storage overflows)
- Encode overshoot time
- Delete fault codes
03 Diagnosis
Diagnosis of the electrical and electronic systems in the 911 Carrera is carried out by means of the Porsche diagnosis systems.
TECHNICAL MANUAL: The diagnosis options are described in the corresponding Technical Data.
Diagnosis socket assignments:
NOTE: The geometry and pin assignments of the diagnosis socket correspond to standards SAE J 1962 and ISO 15031-3.
In order to minimise closed-circuit currents during prolonged transportation of the vehicle and during the production process, after activation of transport/ production mode all functions of the control units which are not directly necessary (e.g. comfort functions) are deactivated. New vehicles are released from production mode via the PIWIS tester.
Fast sleep mode
In order to enable swift closed circuit current measurement, all control units feature a diagnosis facility entitled "fast sleep mode". After activation of this mode by the tester, all control units terminate their activities after terminal 15 "off" in < 5 seconds plus any one-off overshoot times. Safety-critical functions and component protection have priority, however.
The control units on the CAN Comfort bus and the CAN Display bus transmit their sleep standby mode via the bus immediately after the end of the overshoot time and also terminate their activities after bus non-operation.
Prerequisites for activation of fast sleep mode:
- Terminal 15 "on"
- Vehicle speed = 0 km/h
Specified installation list
A specified installation list is cyclically transmitted from the gateway controller into all bus systems The control units are able to carry out automatic self-parameterisation on the basis of this message (e.g. CAN timeout monitoring).
Actual installation list
An actual installation list in which all networked control units enter their configurations (MOST or CAN control units) is stored in the gateway controller.