MOST DATA FRAME Volvo C30 I рестайлинг

MOST DATA FRAME

A data frame consists of different parts. This contains for example

1. control data
2. asynchronous data
3. synchronous data and
4. administrative data.

A data frame on the MOST network is 64 bytes. The data frame consists of the following

1. synchronization of the clock on the MOST network, i. e. the frequency at which data is transmitted so that the data is sent at the correct intervals
2. administrative data, indicates the size of the asynchronous and synchronous data
3. synchronous data
4. asynchronous data
5. control data
6. administrative data.

16 data frames are required to form a block. One block is the minimum size of a MOST message.

All activations on the MOST network are control messages or MOST messages. The majority of the MOST messages are initiated by the infotainment control module . The infotainment control module informs certain control modules if a function in the control module must be activated. The infotainment control module then allocates space to transmit data on the MOST network for those activations which have been initiated in the control modules. This is either synchronous or asynchronous data. The structure of a message is as follows

1. DeviceID. FBlockID. InstID. FktID. OPType

This means

1. The ID number of one of more control modules in the network
2. the ID number of a function unit, for example the CD function in the Integrated Audio Module
3. ID number to differentiate two identical function units
4. The ID number of the function to be activated, for example play or stop
5. Specifies how the function is to be used, because a function can be used in different ways.

The message may appear as follows

1. IAM. CD.01. Track, Length. Set(10)

This means: play song number 10 on the CD player in the Integrated Audio Module (IAM).

The infotainment control module (ICM) knows which control modules are in the MOST network. It can then assign specific ID numbers to all control modules and the included functions. If control modules are removed or added, the ID numbers for the control modules are re-assigned.

The number of "ones" and "zeros" transmitted per second determines the transfer rate.

The number of data frames multiplied by the clock frequency of a frame gives the transfer rate.

Example

The maximum transfer rate of asynchronous data

Bit = a binary 1 or 0

Byte = 8 bit

Maximum asynchronous data = 36 byte

This gives: 36 x 8 = 288 bit

The clock frequency for a data frame = 48 kHz

The maximum number of bits of asynchronous data x clock frequency for a frame: 288 x 48000 = 14 Mbit/s.

The concept for downloading software is the same as for the CAN network. The CAN uses a PBL (primary boot loader) which is permanently installed in the control module, and a secondary program loading file (SBL - secondary boot loader) which is downloaded into a RAM while the control module is being programmed.

When downloading software for the MOST control modules, a third type of download module is used, GBL (Gateway boot loader). For downloads to the MOST control modules to work, the GBL must be loaded into the infotainment control module (ICM). SBL is used to program the infotainment control module (ICM), in the same way for all other CAN control modules.

GBL downloading

A PROG command is transmitted on the CAN network to all control modules including the infotainment control module (ICM). This command sets all the control modules to reset mode. Before the infotainment control module (ICM) switches to reset mode, it switches off the light to all MOST control modules.

The GBL is then downloaded to a RAM memory in the infotainment control module (ICM). The GBL is then activated and the infotainment control module (ICM) transmits light pulses on the MOST network. The GBL now functions as a connection between the CAN and MOST networks. The GBL sets the MOST control modules to programming mode. All the control modules on the MOST and CAN networks can then be addressed in the same way to download software.

In the event of a total software reload for the control modules on the MOST network, select the MOST network option. Select CAN network for control modules on the controller area network (CAN).

This function is used to make sure that all control modules on the MOST network can be used. When the MOST network starts up, ignition position I, II or III, the infotainment control module (ICM) checks that all control modules on the MOST network have approved serial numbers. If the infotainment control module (ICM) detects that one or more control modules do not have approved serial numbers, these modules will be set to "disable mode". This means that the control module functions cannot be used in the MOST network. The control module only acts as a conduit for the light pulses.

It takes 30 seconds for the infotainment control module (ICM) to check the control modules. This means that non-approved control modules will be disabled after 30 seconds.

1. electrical short-circuits are not possible on the MOST network. This reduces the risk of damage to control modules connected to the network
2. As an optical network, the MOST network does not have problems with EMC (Electro Magnetic Compatibility)
3. the wiring is not sensitive to electrical cross-induction from other wiring
4. The transfer speed of the MOST network is much higher than the CAN network
5. it is easy to add further functions and to install accessories, known as plug and play units.

The control modules in the network are connected to each other and are constructed so that more functionality can be easily added. All that is required to increase functionality is

1. to connect the sensors to the nearest control module
2. to connect the controlled component to the nearest control module
3. to download software to change the configuration and programming of the network.

C30/S40/V50

Scheme 1315

C70

Scheme 1316

The MOST network can consist of up to nine different control modules.

The infotainment control module (ICM) deals with monitoring and communication on the MOST network. The infotainment control module (ICM) is in turn monitored by the central electronic module (CEM) on the CAN network.

The vehicle is always equipped with an Infotainment control module (ICM) and Integrated Audio Module (IAM).

In addition to these two, one or more control modules is/are connected to the MOST loop to obtain the desired functions in the vehicle.

The table below lists all the control modules which may be included in the MOST network.

Explanation

CAN = Controller Area Network, electrical network for communication.

LS CAN = low speed side of the CAN.

MOST = Media Oriented Systems Transport, fiber optic network for communication.

Master control module = Control module which monitors the MOST network.

Slave control module = Control module which supplies the MOST network functions.

Option = Factory installed accessories, during the purchase of a new car.

Accessory = After market installation.

The infotainment control module (ICM) knows which control modules are connected to the MOST network. If any control module on the MOST network ceases to communicate, a diagnostic trouble code (DTC) is stored in the infotainment control module (ICM). There is a diagnostic trouble code (DTC) for every control module on the MOST network for this fault.

Missing communication may be due to an internal fault in the control module or because the function is incorrectly implemented in the control module.

Diagnostic trouble code (DTC) ICM-DC00 is stored in the event of an internal fault in the infotainment control module (ICM) preventing the transmitting and receiving diodes from sending sound pulses on the MOST network.

For faults when messages cannot be sent on the MOST network, diagnostic trouble code (DTC) ICM-DC02 is stored.

Causes of this fault may be that

1. a control module, except the infotainment control module (ICM), has a defective optical connector
2. a control module has an internal fault which means that the optical connection stops working
3. a control module on the MOST network is not powered. If there is no power supply, the optical connector stops transmitting light
4. the optical cable is damaged or there is an open-circuit. This fault can occur if the bend radius of the cable is too small or if the cable is kinked or trapped
5. there is dirt or oil on the optical connectors which impedes the light
6. the connection to a control module has come loose
7. the fiber optic terminals in the connector are cross-connected
8. there is a loose connection because the fiber optical wiring is incorrectly installed or the fiber optic terminal pin has been pressed back in the connector
9. a bridging connector has come loose or is damaged.

Ring break diagnostics are used to remedy diagnostic trouble code (DTC) ICM-DC02. If a break is discovered in the MOST network after running a ring break diagnostic, diagnostic trouble code (DTC) ICM-DC01 will be stored in the infotainment control module (ICM). If this is the case, the position of the open-circuit and control module location, can be read off from the infotainment control module (ICM).

The MOST protocol determines how light pulses or their absence should be interpreted. Each pulse or absent pulse is called a "bit". The number of "bits" transmitted on the MOST network is 24.8 million per second (24.8 Mbit/s).

A bit can be

1. binary 0, i. e. no light pulse
2. binary 1, i. e. light pulse.

The light pulses are transmitted in data frames. A data frame consists of different types of data. The size of a data frame is 64 bytes, which is 64 x 8 = 512 bits.

The data frame has a frequency of 48 kHz. This means that 48000 data frames are sent per second on the MOST network.

The data types which are included in a data frame sent on the MOST network are

1. control data
2. synchronous data
3. asynchronous data
4. administrative data.

Control data

Control data is used to check and to allocate the functions to the control modules and the functions in the MOST network.

The control data message is transmitted from, for example, the infotainment control module (ICM) to another specific control module.

The control data message automatically checks if the receiver has received the signal and that the entire message has been correctly transmitted between the transmitting and receiving control modules.

The size of the control data is 2 bytes per data frame. A block, which consists of 16 data frames, is required for a control message to be sent. This means that the total size of the control message is 32 bytes. A control message is the minimum size of a message to activate or deactivate functions on the MOST network.

Examples of MOST messages are track changes or stop commands on the CD player.

Up to 1000 control data messages can be sent per second.

Synchronous data

Synchronous data is used to transmit data which requires considerable quantities of data in real time, for example to play back sound from the Audio Module (AUD).

The length of the synchronous data message which can be sent may be up to 60 bytes per data frame, although never less than 24 bytes. This gives a transfer rate of up to 23 Mbits per second for data transmitted as synchronous data.

Synchronous data shares the data frame with asynchronous data. The infotainment control module (ICM) controls which control modules transmit synchronous data and which are receivers.

Asynchronous data

Asynchronous data is used to send large quantities of data, such as TCP/IP and digital images, but not in real time.

The length of the message can be up to 36 bytes (synchronous data minimum 24 bytes + asynchronous data 36 bytes = 60 bytes). This gives a maximum transfer rate of 14 Mbits per second. When the message has been sent, a check is run to ensure that is has been correctly received.

Asynchronous data shares the data frame with synchronous data. The infotainment control module (ICM) controls which control modules transmit asynchronous data and which are receivers.

Administrative data

Administrative data consists of two parts.

The first part is at the start of the data frame. This describes how much of the transmitted data is synchronous and how much is asynchronous.

The second part is at the end of the data frame. This part checks that the control modules on the MOST network are working correctly.

The size of administrative data is 2 bytes.

A data frame consists of different parts. This contains for example

1. control data
2. asynchronous data
3. synchronous data
4. administrative data.

A data frame on the MOST network is 64 bytes. The data frame consists of the following

1. synchronization of the clock on the MOST network, i. e. the frequency at which data is transmitted so that the data is sent at the correct intervals
2. administrative data, indicates the size of the asynchronous and synchronous data
3. synchronous data
4. asynchronous data
5. control data
6. administrative data.

16 data frames are required to form a block. One block is the minimum size of a MOST message.

All activations on the MOST network are control messages or MOST messages. The majority of the MOST messages are initiated by the infotainment control module (ICM). The infotainment control module (ICM) informs certain control modules if a function in the control module must be activated. The infotainment control module (ICM) then allocates space to transmit data on the MOST network for those activations which have been initiated in the control modules. This is either synchronous or asynchronous data. The structure of a message is as follows

1. DeviceID. FBlockID. InstID. FktID. OPType

This means

1. DeviceID - ID-number of one or several control modules in the network
2. FBlockID - ID-number of a function unit, for example, the CD-function in the integrated audio module (IAM)
3. InstID - ID number to differentiate two identical function units
4. FktID - The ID number of the function to be activated, for example play or stop
5. OPType - Specifies how function is to be used, since a function can be used in different ways.

The message may appear as follows

1. IAM. CD.01. Track, Length. Set(10)

This means: play song number 10 on the CD player in the Integrated Audio Module (IAM).

The infotainment control module (ICM) knows which control modules are in the MOST network. It can then assign specific ID numbers to all control modules and the included functions. If control modules are removed or added, the ID numbers for the control modules are re-assigned.

The number of "ones" and "zeros" transmitted per second determines the transfer rate.

The number of data frames multiplied by the clock frequency of a frame gives the transfer rate.

Example

The maximum transfer rate of asynchronous data

Bit = a binary 1 or 0

Byte = 8 bit

Maximum asynchronous data = 36 byte

This gives: 36 x 8 = 288 bit

The clock frequency for a data frame = 48 kHz

The maximum number of bits of asynchronous data x clock frequency for a frame: 288 x 48000 = 14 Mbit/s.

The concept for downloading software is the same as for the CAN network. The CAN uses a PBL (primary boot loader) which is permanently installed in the control module, and a secondary program loading file (SBL - secondary boot loader) which is downloaded into a RAM while the control module is being programmed.

When downloading software for the MOST control modules, a third type of download module is used, GBL (Gateway boot loader). For downloads to the MOST control modules to work, the GBL must be loaded into the infotainment control module (ICM). SBL is used to program the infotainment control module (ICM), in the same way for all other CAN control modules.

GBL downloading

A PROG command is transmitted on the CAN network to all control modules including the infotainment control module (ICM). This command sets all the control modules to reset mode. Before the infotainment control module (ICM) switches to reset mode, it switches off the light to all MOST control modules.

The GBL is then downloaded to a RAM memory in the infotainment control module (ICM). The GBL is then activated and the infotainment control module (ICM) transmits light pulses on the MOST network. The GBL now functions as a connection between the CAN and MOST networks. The GBL sets the MOST control modules to programming mode. All the control modules on the MOST and CAN networks can then be addressed in the same way to download software.

In the event of a total software reload for the control modules on the MOST network, select the MOST network option. Select CAN network for control modules on the controller area network (CAN).

This function is used to ensure that all control modules on the MOST network can be used. When the MOST network starts up, ignition position I, II or III, the infotainment control module (ICM) checks that all control modules on the MOST network have approved serial numbers. If the infotainment control module (ICM) detects that one or more control modules do not have approved serial numbers, these modules will be set to disable mode. This means that the control module functions cannot be used in the MOST network. The control module only acts as a conduit for the light pulses.

It takes 30 seconds for the infotainment control module (ICM) to check the control modules. This means that non-approved control modules will be disabled after 30 seconds.

1. electrical short-circuits are not possible on the MOST network. This reduces the risk of damage to control modules connected to the network
2. As an optical network, the MOST network does not have problems with EMC (Electro Magnetic Compatibility)
3. the wiring is not sensitive to electrical cross-induction from other wiring
4. The transfer speed of the MOST network is much higher than the CAN network
5. it is easy to add further functions and to install accessories, known as plug and play units.

The control modules in the network are connected to each other and are constructed so that more functionality can be easily added. All that is required to increase functionality is

1. to connect the sensors to the nearest control module
2. to connect the controlled component to the nearest control module
3. to download software to change the configuration and programming of the network.

Each control module in the MOST network has an optical connector which consists of two diodes, a sender diode and a receiver diode. These transmit and receive light pulses.

The actual communication between two control modules is as follows. A sender diode transmits the message as a light pulse. This is transmitted from the control module via the MOST network to a photo-optical receiver diode in the receiving control module.

The two optical terminals in the connector are numbered in the same way on all control modules in the MOST network. The size of the plastic housing for the two optical terminals varies. A connector with integrated power supply is integrated with the optical terminals and one connector with only the optical terminals.

All messages are transmitted as light pulses in the same direction on the MOST network. This means that if other control modules are connected between the two control modules which are communicating, the light pulses pass through these with no effect on the information. The control modules which are passed through amplify the light pulse so that it does not become too weak.

A control module with an internal fault can be set to bypass mode. In this mode, the light pulses are sent straight through the control module without the control module amplifying the light pulse. This means that the distance before the light pulse is amplified is longer and therefore the luminance is weaker. If the light pulse is too weak, it cannot be received by the receiving control module.

The infotainment control module (ICM) is the gateway between the MOST and CAN networks for communication to and from control modules connected on the CAN network.

The infotainment control module (ICM) monitors the communication on the MOST network. This involves distributing sound channels on the MOST network, so that sound data can be distributed from, for example, the Remote Digital Audio Receiver (RDAR) to the Integrated Audio Module (IAM). The majority of activations on the MOST network are initiated by the infotainment control module (ICM).

The infotainment control module (ICM) also manages diagnostic trouble codes (DTCs) on the MOST network.

If a control module on the MOST network stops working and is unable to transmit light pulses onwards, or if there is an open-circuit in the fiber optic cable, the entire MOST network will stop working. This means that all the control modules on the MOST network will stop working. For further information about remedying this, see: FAULT MANAGEMENT ON THE MOST NETWORK

The infotainment control module (ICM) must always be connected on the MOST network for communication on the MOST network to work.

The MOST network connections increase and the signal routing may change when control modules are added because adapter wiring is used to connect the new control module.

This function can be used to read parameters, status identifiers and counters stored at the same time as a diagnostic trouble code (DTC). These are called frozen values.

New software can be downloaded into the multimedia module (MMM). When ordering software, the hardware and the software in the car is compared to the information in the Volvo central database. If the comparison is OK the software is downloaded to the control module.

If the comparison between the car and Volvo central database is not OK, the database is updated with the car configuration. When this is complete the software is downloaded.

All the software required for the traffic information system to work in the control module is on the DVDs.

The control module is located in the glove compartment.

After replacing the control module, the unique serial numbers of the control module are checked by the infotainment control module (ICM). The installed control module will not work if the serial number is incorrect.

Try turning the ignition off and on if there are problems after the software is downloaded and the control module is not working.

The MOST network is used for a total software reload.

Scheme 1317

The on-screen menu can be controlled using the buttons on the reverse of the steering wheel.

The buttons consists of

1. a Back button
2. an Enter button
3. a navigation button which is used to move the cursor up, down, left and right on the screen.

The steering wheel module (SWM) (3/254) transmits a signal to the infotainment control module (ICM) (16/1) via the controller area network (CAN).

The infotainment control module (ICM) converts the electrical signal to an optical signal and sends it onwards to the multimedia module (MMM) (16/108) via the MOST network.

The remote control for the multimedia module (MMM) has the same functions as the steering wheel buttons. The remote control can be used to control the menus on the display screen. The IR signal is transmitted from the remote control to an IR receiver which is mounted in the loudspeaker grille on the dashboard. The receiver transmits the signal to the multimedia module (MMM) via the infotainment control module (ICM).

Scheme 1318

The navigation function displays the location of the car and directions to the entered destination.

The navigation buttons on the steering wheel module (SWM) (3/254) are used to control the on-screen menu for navigation.

The multimedia module (MMM) (16/108) receives GPS signals on the MOST-network from the global positioning system module (GPS) (16/139).

Two signals are transmitted to the central electronic module (CEM) (4/56) on the high speed section of the control area network (CAN)

1. information about the wheel rotation counter is transmitted from the brake control module (BCM) (4/16)
2. information about the back-up gear position is transmitted from the transmission control module (TCM) (4/28).

The central electronic module (CEM) transmits both signals to the infotainment control module (ICM) (16/94) via the low speed side of the Controller area network (CAN). The vehicle speed signal is transmitted from the central electronic module (CEM) to the infotainment control module (ICM). The infotainment control module (ICM) transmits in turn the signals to the multimedia module (MMM) on the MOST network.

Information for voice guiding for the selected destination is transmitted on the MOST network between the multimedia module (MMM) and the audio module (AUD) (16/105).

A DVD with the required road network must be inserted in the DVD player in order for the multimedia module (MMM) to select a route and display the position of the car. The control module is then able to calculate the position and display it on the directly connected screen (16/46).

The multimedia module (MMM) is an option and has the primary task of the managing the functions for

1. navigation
2. Traffic message channel (TMC)
3. FM multiplex (Japan only)
4. display screen
5. DVD player.

Only the display screen is directly connected to the multimedia module (MMM). The DVD player is integrated in the multimedia module (MMM). The functions from other control modules are via the MOST network, but are managed using the multimedia module (MMM). The system is not compatible with music or film CD or DVDs.

The multimedia Module (MMM) uses the MOST network to communicate with other control modules.

The control module checks activations and input and output signals via an integrated diagnostic system. A diagnostic trouble code (DTC) is stored if the control module detects a fault. Any diagnostic trouble codes (DTCs) are stored in the control module memory. This information can be read off using VIDA (Volvo scan tool) via the data link connector (DLC) in the vehicle.

In order to work correctly on the MOST network, the infotainment control module (ICM) checks that the serial number in the multimedia module (MMM) is correct. The multimedia module (MMM) will not function if the serial number is incorrect. Try switching the ignition off and on if there are problems when replacing the multimedia module (MMM).

A simple way to ensure that the multimedia module (MMM) is powered is to insert and then remove a DVD. If this does not work, check that the control module is powered and grounded.

The multimedia module (MMM) is located in the glove compartment.

For further information, also see SIGNALS .

The table below summarizes the input signals to and output signals from the multimedia module (MMM). The signal types are divided into directly connected signals and MOST communication. The illustration below displays the same information with the Volvo component designations.

Scheme 1319

Scheme 1320

The Multimedia module (MMM) has a hard disk and a DVD player integrated in the control module. The DVD player is used to upgrade the software in the Multimedia module (MMM) and transfer map information from the DVD to the hard disk. Using the hard disk obtains the map information quicker and makes storing more data possible. The map information is used for navigation.

The Multimedia module (MMM) has an integrated gyro that manages information about the vehicle's direction of travel.

The multimedia module (MMM) as inputs and outputs for

1. power supply
2. ground
3. GPS
4. TMC
5. RGB output to the screen
6. MOST network

GPS

Information to the GPS unit consists of signals received from GPS satellites via the GPS antenna.

The navigation system requires at least three satellites to be able to calculate the vehicle's position.

Power is supplied to the GPS unit from the multimedia module (MMM). The GPS unit is integrated in the multimedia module (MMM).

Note. If the GPS signal is diagnosed as missing, the signal should be checked outdoors in an open area as the signal could be blocked if the vehicle is indoors and surrounding buildings could interfere with reception of GPS signals. It can take up to 12 minutes until the GPS signal has been captured and the position has been determined.

TMC

The TMC signal is transmitted from the antenna amplifier and received by the TMC receiver. The TMC signal is managed in the Multimedia module (MMM) and the information is then presented on the display screen.

The TMC receiver is integrated in the multimedia module (MMM).

TMC is a standardized code system for traffic bulletins, such as information on road construction. TMC is only available on certain markets.

Scheme 1321

Functions such as system settings and navigation are presented on the display screen in the center of the dashboard. The Multimedia module (MMM) transmits RGB signals to the display screen.

If there is an internal fault in the screen or faults in communication with the control module, the quality of the display on the screen will deteriorate or the screen will stop working completely. A simple way to detect a fault in the screen, or communication problems between the screen and the control module, is to check the appearance of the image on screen.

The screen's menu system can be controlled with the navigation keys on the back of the steering wheel or with the remote control for the screen.

The receiver for the remote control, the IR-eye, is installed in the speaker grill on the instrument panel.

This function is used to read the status or value of parameters. The status or value can be presented digitally.

This function can be used to activate components and functions that affect the multimedia module (MMM).

This function can be used to read out parameters, identify status and counts stored at the same time as a diagnostic trouble code (known as frozen values).

The DVD is used to upgrade the application software in the multimedia module (MMM).