The safety system involves functions such as:
The individual functions are specified in the relevant functional descriptions.
The BYTEFLIGHT bus system has a star-shaped structure. The individual satellites (= control units with/without sensors) are interconnected across a star coupler by means of fibre-optic cables. The star coupler in the BYTEFLIGHT bus system is the Safety and Information Module (SIM) or the Safety and Gateway Module (SGM). Depending on the vehicle, the star coupler is the SIM or the SGM. In the rest of the description, both the SIM and SGM will be mentioned.
Example:
There is a transmission and a reception module (transmitter and receiver) as a unit in each satellite for connecting to the BYTEFLIGHT bus. The unit has an integrated transmit and receive diode.
The safety system uses data from internal and external sensors.
Self-test on switching on terminal R: a self test is run when terminal R is switched on. This self test takes a maximum of approx. 10 seconds. The entire safety system is checked during this self-diagnosis phase.
Fault detected in the system: If the SIM or SGM detects a fault during the self-test, the self-test takes a maximum of approx. 1 minute. The airbag warning lamp remains on after the 10 seconds if a fault is detected.
System without faults: if no fault is detected in the system, the airbag warning lamp goes out again.
The safety system assumes standby mode as soon as the self test is completed.
Monitoring during vehicle operation: during vehicle operation, the individual satellites continuously monitor themselves. Here, the following checks are performed:
Activation of the trigger circuits requires acceleration values, seat occupancy recognition, seat belt buckle monitoring etc. All the information is placed as a message on the BYTEFLIGHT bus and evaluated by the SIM or SGM. The SIM or SGM, as BYTEFLIGHT bus master, decodes on the basis of all the available sensor data when the BYTEFLIGHT bus is to be set into a triggerable state. This ”Trigger mode” places all the actuators of the safety system in the triggerable state.
To trigger a priming stage, two fully separate and independent signal and decision paths are required: For triggering
The trigger circuits are checked
Faults are indicated via the airbag warning lamp.
The individual satellites send information regarding the control unit status to the SIM or SGM, The SIM or SGM evaluates the incoming information and then activates accordingly
In the event of a fault:
The specified range for the power supply from the SIM or SGM to the satellites is: 9 V - 11 V. The SIM or SGM switches off the power supply to individual satellites after about 4 seconds if
If a satellite is unplugged, the power supply from the SIM or SGM to that satellite is thus also switched off. In order to be able to measure that output voltage from the SIM or SGM, the output must first be activated.
Example: output voltage from the SIM or SGM is to be measured. The following procedure must be used:
This sequence is run automatically in the test program. The sequence is explained to prevent incorrect measurements (e.g. with multimeter) and thus unnecessary replacement!
The following additional information regarding the individual fault code memory entries can be obtained:
Fault duration: The fault duration is used for the classification of a fault on the basis of the duration of the uninterrupted occurrence or detection by the control unit. The entry of the classification takes place when a fault disappears or on transition of the control unit into the ”Sleep mode”. If a fault occurs with different classifications, the different classifications are stored.
Fault start system time: The Fault start indicates the time at which the fault occurred the first time. The system time is initialised by a diagnostic system command during production of the vehicle.
Fault end system time: The fault end specifies the time at which the fault disappears. If the fault is present at the moment, then fault end system time = fault start system time.
If the fault code memory is deleted after work on the vehicle, it can occur that the airbag warning lamp lights up, but no fault is stored in the fault code memory of the BYTEFLIGHT control units. Even after ignition off and ignition on, the airbag warning lamp does not go out and there is no fault code memory entry. The following procedure is required if this occurs:
E65, E66, E67, RR01:
E85:
E60, E61, E63, E64:
Following this, information on the fault should be available in the BYTEFLIGHT control units.
In the test programs, the following instructions are given for certain faults:
Notes on 2.: switch to the control unit function of the relevant satellite and erase the fault memory.
Notes on 3.: switch to SIM or SGM control unit function. Under 'Component activation', start the self test (the self test is a test of the overall safety system). This operation is necessary so that any faults currently present are stored!
Notes on 4.: switch to SIM or SGM control unit function. Under diagnosis requests, observe end of self test (after self test ended, continue with 5.)
Notes on 5.: switch to the control unit function of the relevant satellite and read the fault memory.
In all cases, only perform work on the fuel pump with the ignition off!
All work on the airbags must be carried out with the battery disconnected!
Connect and disconnect all BYTEFLIGHT control units, sensors and generators only with the battery disconnected!
If a fibre-optic cable on the BYTEFLIGHT bus has to be repaired, it must be borne in mind that there may only be one join in a fibre-optic cable. If there is already a join due to a door connector, the fibre-optic cable must not be repaired. In the case of a defect, the fibre-optic cable must be replaced!