Safety and Gateway Module, Supply (SGM-SIM Safety and Gateway Module (SIM))

Safety System And BYTEFLIGHT Bus General Functional Description

The safety system involves functions such as:
- Battery terminal isolation
- Airbag activation
- Seat belts
- Seat occupancy detection.

The individual functions are specified in the relevant functional descriptions.

Brief description of components

BYTEFLIGHT bus and star connector SIM or SGM
The BYTEFLIGHT bus system has a star-shaped structure. The individual satellites (= control modules with/without sensors) are interconnected across a star connector by means of fiber-optic cables. The star connector 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 connector is the SIM or the SGM. In the rest of the description, both the SIM and SGM will be mentioned.

Example:
- E65/E66/E67/RR01: Star connector for Safety and Information Module (SIM)
- E85: Star connector for Safety and Information Module (SIM)
- E60/E61/E63/E64: Star connector Safety and Gateway Module (SGM)

Satellites/control modules
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.

Sensors
The safety system uses data from internal and external sensors.
- Internal sensors: fitted in the BYTEFLIGHT control modules, e.g. acceleration sensors
- External sensors: fitted outside the BYTEFLIGHT control modules, e.g. belt buckle switch

Main functions

Self test
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.
- During this self test, the safety system cannot be activated.
- It is not possible to code and clear the fault memory.
- The airbag warning lamp lights up.

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:
- Checking the optical signal quality
- The receiver provides the possibility to diagnose the optical signal reception quality. Here, a warning signal is generated when the optical receiving power falls below a certain threshold. The communication still functions without faults. If this warning signal occurs during operation, an entry is made in the fault memory.

- Check of the safety-related bus messages
- Checking the ignition circuits for short circuit and interruption

Activating the trigger circuits
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 mode" must be set by the SIM or SGM on the BYTEFLIGHT bus and
- there must be activation of the satellite to be triggered according to specific algorithms in each case (from each satellite).

Self-diagnosis of trigger circuits
The trigger circuits are checked
- during the self test with terminal R ON and
- while driving

Faults are indicated via the airbag warning lamp.

Airbag warning lamp and Check Control messages
The individual satellites send information regarding the control module status to the SIM or SGM, The SIM or SGM evaluates the incoming information and then activates accordingly
- the airbag warning lamp
- the check control messages in the information display of the instrument cluster. The generated display information for the check control is transferred by the SIM or SGM in cycles to the instrument cluster.

In the event of a fault:
- If the bus communication to the individual satellites is interrupted, messages are generated in the SIM or SGM. This is also the case during the self test.
- If the instrument cluster receives no display information for a period of 2 seconds, the airbag warning lamp is activated.

SIM or SGM output voltage
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
- the bus communication is disrupted (e.g. fiber-optic cable defective) or
- the leads to the power supply are defective.

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:
- Terminal 15 On, i.e. ignition on
- for voltage measurement, connect the adapter to SIM or SGM
- switch to control-module functions SIM or SGM
- component activation: output voltages and light (diodes)
(activation for 4 seconds)
- Measure voltage

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!

Fault memory
The following additional information regarding the individual fault memory entries can be obtained:
- Fault duration t > 1 min
- Fault duration 1 s < t < 1 min
- Fault duration 0 < t < 1 s
- Fault start system time, e.g. 5.34 h
- Fault end system time, e.g. 5.38 h

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 module. The entry of the classification takes place when a fault disappears or on transition of the control module 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 initialized 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.

Fault symptom: airbag warning lamp lights up, but there is no fault memory entry
If the fault memory is cleared after work on the vehicle, it can occur that the airbag warning lamp lights up, but no fault is stored in the fault memory of the BYTEFLIGHT control modules. Even after ignition off and ignition on, the airbag warning lamp does not go out and there is no fault memory entry. The following procedure is required if this occurs:

E65, E66, E67, RR01:
- Ignition Off
- Let the vehicle "sleep" (start/stop button no longer lights up)
- Ignition on
- Run a short test

E85:
- switch to the control-module function of the Safety and Information Module (SIM).
- SIM: component activation: start self test
- SIM: diagnosis requests: observe end of self test
- Run a short test

E60, E61, E63, E64:
- Ignition Off
- Allow the vehicle to "go to sleep" (operate child lock switch in the switch block of the driver's door. The diode of the button lights up. When the light goes out, the vehicle has "gone to sleep")
- Ignition on
- Run a short test

Following this, information on the fault should be available in the BYTEFLIGHT control modules.

Control-module functions
In the test programs, the following instructions are given for certain faults:
1. Switch to 'Control-Module Functions' and perform the following steps:
2. Satellite: Clear fault memory
3. SIM or SGM: component activation: start self test
4. SIM or SGM: diagnosis requests: observe end of self test
5. Satellite: Read fault memory

Notes on 2.: switch to the control-module function of the relevant satellite and clear the fault memory.

Notes on 3.: switch to SIM or SGM control-module 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-module function. Under diagnosis requests, observe end of self test (after self test ended, continue with 5.)

Notes on 5.: switch to the control-module function of the relevant satellite and read the fault memory.

Service functions

Notes on safety
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 modules, sensors and generators only with the battery disconnected!

If a fiber-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 fiber-optic cable. If there is already a join due to a door connector, the fiber-optic cable must not be repaired. In the case of a defect, the fiber-optic cable must be replaced!