AUTOTMOTIVE BUS
Posted: 29 Mar 2011, 21:12
Note: There are six classifications of vehicle Buses: Class A, Class B, Class C, Emissions/Diagnostics, Mobile Media, and X-by-Wire. Many of the buses listed below have a notation defining what class they reside in.
Class A: A multiplex wiring system which reduces wiring by transmitting and receiving multiple signals over the same signal bus. The multi-purpose bus replaces individual wires performing the same function.
Normally Class A defines general purpose UART communication with bit rates below 10kbps
Class B: A multiplex wiring system which transmits data between nodes. The nodes replace existing stand-alone modules. Used as a non-critical 10kbps to 125kbps bus
Class C: A multiplex wiring system which reduces wiring by using real-time high-data signals. Operating between 125kbps and 1Mbps
Emissions/Diagnostics: handle either Emissions or Diagnostics buses.
Mobile Media: buses handle Mobile Media equipment.
X-by-Wire: is the collective term for the addition of electronic systems into the vehicle to enhance and replace tasks that were previously accomplished via mechanical and hydraulic systems.
Automotive temperature requirements are -40C to +125C.
In addition, a number of the listed buses define the Electrical Physical layer and the Optical Physical layer, which is normal for a bus which defines both interface types. The Physical interface bus being either fiber [Optical] or wire [electrical]. The difference here, in some cases, is that the electrical interface being defined resides just prior to the optical encoder. So the Physical interface bus from device to device is optical [fiber], but the specification also defines the Physical [electrical] interface into the optical transmitter/receiver [which is not normally done outside of Automotive buses].
Also: ... "It is becoming clear that regardless of carmaker, new vehicles will be made using LIN for the lowest data-rate functions, CAN for medium speed, MOST for the high-speed data rates and FlexRay, for safety-critical applications such as steer- and brake-by-wire." from Automotive Industries.
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MOST bus Description
MOST bus: [Media Oriented Systems Transport],defines a multimedia fiber-optic (low overhead, low cost) point-to-point network implemented in a ring, star or daisy-chain topology over Plastic optical fibers [POF].
The MOST bus specifications define the Physical [Electrical and Optical parameters] Layer as well as the Application Layer, Network Layer, and Medium Access Control.
The MOST bus provides an optical solution for automotive media [entertainment] networks [Video, CD..].
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J1850 bus Description
The SAE J1850 bus is used for diagnostics and data sharing applications in On and Off road vehicles. The J1850 interface takes two forms; A 41.6Kbps Pulse Width Modulated (PWM) two wire differential approach, or a 10.4Kbps Variable Pulse Width (VPW) single wire approach. The single wire approach may have a bus length up to 35 meters (with 32 nodes). The J1850 interface was developed in 1994, J1850 may be phased out for new designs. The J1850 is a class B protocol. The J1850 protocol uses CSMA/CR arbitration. The frame consists of a Start Of Frame [SOF], which is high for 200uS. The Header byte follows the SOF and is one byte long.
The data follows the header byte. The one byte CRC [Cyclical Redundancy Check] follows the data field.
After the CRC an End Of Data [EOD] symbol is sent. The EOD is sent as a 200uS low pulse.
{Back to Automotive Bus Index}
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MI Bus Description
MI Bus (MI Bus [Motorola Interconnect] is a serial [Single wire] communications protocol with one Master and many Slaves.
The MI bus may applied to drive Mirrors, Seats, Window lifts or Head light levellers. The Master sends address and data [the Push Field] to all slaves on the bus.
The slave with the same address responds with the information requested [the Pull Field].
The Push field contains a Start bit [low for 3 bit times], a synchronization bit [bi-phase encoded 0], a data field [5 bits bi-phase encoded], and an address field [3 bits bi-phase encoded].
The Pull field contains a synchronization bit [bi-phase encoded 1], the data field [3 bits encoded NRZ], and a End of frame field [~ 3 cycles of a 20KHz square wave].
The single wire line operates between Logic 0 [0.3v maximum], and Logic 1 [+5 volts].)
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DSI Bus Description
DSI Bus [Distributed Systems Interface] developed by Motorola as a dedicated safety bus.
DSI is a two-wire serial bus linking safety-related sensors and components in vehicles.
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BST Bus Description
BST Bus [Bosch-Siemens-Temic] is another vehicle safety bus, used with air-bags (for example).
The BST bus is a 2-wire bus using Manchester encoding and either Parity or CRC for error correction and detection. The BST bus runs up to a maximum of 250Kbps.
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MML Bus Description
MML Bus [Mobile Multimedia Link] is multimedia bus.
The MML Bus uses plastic optical fiber technology in a star architecture via a Master/Slave communication approach.
MML Bus has an operation speed of 100Mbit/sec with a maximum cable length of 10 meters [that can't be right]. Encoding for MML is NRZ.
The MML bus is fault tolerant and handles plug and play.
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byteflight (SI-Bus) Description
byteflight is used for safety-critical applications in motor vehicles [air-bags]. Byteflight is a TDMA [Time Division Multiple Access] protocol that runs at 10Mbps over [2-WIRE or 3-WIRE] Plastic optical fibers [POF] in a bus, Star or Cluster configuration which provides an information update rate of 250uS. Byteflight is based on a message-oriented transmission process, with Master/Slave media access [all messages are made available to all bus subscribers at the same time]. The frame consists of a 6-bit Message Start sequence, an 8-bit message identifier [ID], one length byte [LEN], up to 12 data bytes can be transmitted in the following data field [D0 to D11].
After the data field a 2-byte [16-bit] CRC-sequence is sent [CRCH/CRCL].
{Automotive Bus Index}
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FlexRay Description
FlexRay is a high-speed serial [Synchronous and Asynchronous] communication system for in-vehicle networks [Control Systems] using Point-to-Point [Star topology] links, at 10Mbps [Fault-Tolerant] over Un-shielded Twisted Pair [UTP] or Shielded Twisted Pair [STP] cable.
The FlexRay bus defines the Physical layer [Electrical and Optical] and Protocol.
FlexRay is an extended protocol version of byteflight. Applications for FlexRay include; steer-by-wire and brake-by-wire.
{Automotive Bus Index}
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domestic digital data bus (D2B) Description
Domestic Digital Bus [D2B] is an optical data bus system connecting audio, video, computer peripheral and telephone components in a single ring structure within the vehicle.
Mercedes-Benz uses a combination ring and Star optical [650nm] topology at a speed of 5.6MBps [20MBps maximum].
The D2B interface has a maximum fiber distance of 10 meters [1 coupler] or 7 meters [2 couplers].
{Automotive Bus Index}
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SMARTwireX Description
SMARTwireX defines an electrical physical layer (PHY) supporting D2B networks running up to 25Mbps.
SMARTwireX runs over standard low-cost UTP cabling, with full automotive EMC compatibility.
SMARTwireX is an electrical physical layer solution for automotive networks.
Initially designed for D2B electrical networks, but potentially capable of supporting other networks as well.
SMARTwireX uses a Master/Slave approach connected via twisted pair, encoded as PWM. SMARTwireX has a maximum bus length of 150m [meters].
{Automotive Bus Index}
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IDB-1394 Bus Description
The IDB-1394 Bus is the Automotive version of the IEEE 1394 {Firewire}.
"IDB-C was the first of a family of in-vehicle serial communication protocol networks. IDB-C is defined in the SAE J2366 - ITS Data Bus series of specifications.
IDB-C is based on CAN 2.0B (Controller Area Network) silicon and physical layer, specifically on SAE J2284 - High Speed CAN."
There are four layers of the IDB protocol stack; J2366-1, Physical Layer, J2366-2, Link Layer, J2366-4, Thin Transport Layer, J2366-7, Application Message Layer.
The IDB is primarily used as a consumer device bus operating over an unshielded Twisted Pair [UTP] multidrop cable.
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IEBus Description
Inter Equipment Bus [IEBus] is used as an In-vehicle bus support using half duplex asynchronous [Multi-Master] communication with CSMA/CD for access control.
Two differential lines are used; Data+ / Data-. Two modes are defined: Mode 0 uses 16 bytes/frame and runs at 3.9kbps [6MHz Osc.] or 4.1kbps [6.29MHz Osc.].
Mode 1 uses 32 bytes/frame and runs at 17kbps [6MHz Osc.] or 18kbps [6.29MHz Osc.]. The IEbus allows 50 units on the bus over a maximum length of 50 meters.
The cable capacitance is rated to have 8000pF max [6MHz] or 7100pF max [6.29MHz]. The bus is terminated to 120 ohms. Each device on the bus has a 12 bit address.
The IEBus was developed by NEC Electronics. For a detailed description, and circuit Interface implementation; see the IEbus Interface page
{Automotive Interface Bus Index}
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LIN Bus Description
Local Interconnect Network [LIN] is used as an in-vehicle communication and networking serial bus between intelligent sensors and actuators.
The LIN specification covers the transmission protocol [Physical Layer and the Data Link Layer of LIN], and the transmission medium.
The LIN Bus is a class A protocol operating at a maximum bus speed of 19200 baud over a maximum cable length of 40 meters.
The specification may be obtained from LIN Consortium.
For a detailed description, Engineering Data, and circuit Interface implementation; see the LIN Bus page.
{Automotive Interface Bus Index}
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CAN Bus Description
CANbus Transceiver CAN Bus. A vehicle may have one or more CANbus implementations. An application for a low speed CANbus may include operate window and seat controls. A high speed CANbus may be employed for engine management or brake control, in addition to other applications.
The Controller Area Network (CAN) specification defines the Data Link Layer, ISO 11898 defines the Physical Layer. The CAN interface is an asynchronous transmission scheme controlled by start and stop bits at the beginning and end of each character. This interface is used, employing serial binary interchange. A class B, and Class C bus. Information is passed from transmitters to receivers in a data frame. The data frame is composed of an Arbitration field, Control field, Data field, CRC field, ACK field. The frame begins with a 'Start of frame', and ends with an 'End of frame' space. The data field may be from 0 to 8 bits.
The frame check sequence is derived from a Cyclic Redundancy Code (CRC);
the coefficients are generated modulo-2: X15 + X14 + X10 + X8 + X7 + X4 + X3 + 1
For additional information refer to: CAN Specification; Version 2.0, or ISO 11898/11519
Controller Area Network (CAN); ISO 11898/11519.
For a detailed description, Engineering Data, circuit Interface implementation and specifications; see the CANbus page.
The CAN bus page also lists additional protocols based on CAN bus.
{Automotive Interface Buses Index}
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Intellibus Description
Intellibus is a multi-drop communications bus developed by Boeing initially for military avionics applications, but also has an application in the automotive field. Similar to CAN in concept with similar limitations and inefficiencies. Intellibus operates at bus speeds of 12.5Mbps. Intellibus is used with electronic engine control, transmission, and other vehicle systems as another Drive-by-Wire protocol.
Intellibus uses a Master/Slave approach with Manchester Bi-Phase bit encoding over a twisted pair wire. The maximum bus length is 30 meters, at 12.5Mbps to a maximum of 64 nodes.
Intellibus provides both parity and CRC error detection. A class B, and Class C bus.
{Automotive Buses Index}
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OBDII Bus Description
OBDII Cable OBD2 [On-Board Diagnostics II] defines a communications protocol and a standard connector to acquire data from passenger cars. It was required by U.S. EPA on all gasoline powered cars and light duty trucks manufactured for the U.S. after 1996 to help monitor/inspect vehicle emissions.
OBDII will light a lamp called a MIL (malfunction indicator lamp), also known as the "check engine" light on the dash.
The OBD-II standard allows for multiple electrical interfaces, which complicates the hardware used to interface with the vehicle. OBDII data as defined by the SAE J1979 standard
SAE J1708 Bus Description
Serial Data Communications Between Microcomputer Systems in Heavy-Duty Vehicle Applications. J1708 defines the physical layer only. J1708 uses the RS485 bus as the electrical layer.
The cable is a 2-wire 18 AWG wire with a maximum distance of 40 meters. Class A operating to 9600bps. A message starts with a Message Identification Character [MID], followed by Data characters and then a checksum.
The total message length is 21 or less characters. Each character is 10 bits, each character begins with a Start bit [logic low].
{Automotive Buses Index}
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Vehicle Area Network
VAN An automotive bus developed by Peugeot and Renault [early 1990's].
The VAN bus is a differential bus with Enhanced Manchester Data Encoding.
The Two-wire data bus consists of 'Data' and 'DataB'.
The VAN network may have one or more Masters and some number of Slaves.
The VAN Networking Topology may be interconnected in a number of different architectures.
VAN may be either a BUS, Ring, Tree or Star style using broadcast or point-to-point communications.
ISO standard 11519-3 [VAN Protocol]. Transmission speed 160kHz [estimate].
IC Interface MTC-30521, Alcatel. VAN Data Link Controller TSS461F, Atmel.
The resistors [R2] shown in the graphic are for impedance balance of the VAN Bus.
Resistors R1 and Capacitors C1 form a low pass filter [Ri / RiB] which then feeds the comparators.
The normal circuit output is from Ro. However is either Data or DataB fail, the output can still be reconstituted.
The Ro can be used with one of the two supplementary comparators [either R1 or R2] to allow communication, even though one line has failed.
Class A: A multiplex wiring system which reduces wiring by transmitting and receiving multiple signals over the same signal bus. The multi-purpose bus replaces individual wires performing the same function.
Normally Class A defines general purpose UART communication with bit rates below 10kbps
Class B: A multiplex wiring system which transmits data between nodes. The nodes replace existing stand-alone modules. Used as a non-critical 10kbps to 125kbps bus
Class C: A multiplex wiring system which reduces wiring by using real-time high-data signals. Operating between 125kbps and 1Mbps
Emissions/Diagnostics: handle either Emissions or Diagnostics buses.
Mobile Media: buses handle Mobile Media equipment.
X-by-Wire: is the collective term for the addition of electronic systems into the vehicle to enhance and replace tasks that were previously accomplished via mechanical and hydraulic systems.
Automotive temperature requirements are -40C to +125C.
In addition, a number of the listed buses define the Electrical Physical layer and the Optical Physical layer, which is normal for a bus which defines both interface types. The Physical interface bus being either fiber [Optical] or wire [electrical]. The difference here, in some cases, is that the electrical interface being defined resides just prior to the optical encoder. So the Physical interface bus from device to device is optical [fiber], but the specification also defines the Physical [electrical] interface into the optical transmitter/receiver [which is not normally done outside of Automotive buses].
Also: ... "It is becoming clear that regardless of carmaker, new vehicles will be made using LIN for the lowest data-rate functions, CAN for medium speed, MOST for the high-speed data rates and FlexRay, for safety-critical applications such as steer- and brake-by-wire." from Automotive Industries.
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MOST bus Description
MOST bus: [Media Oriented Systems Transport],defines a multimedia fiber-optic (low overhead, low cost) point-to-point network implemented in a ring, star or daisy-chain topology over Plastic optical fibers [POF].
The MOST bus specifications define the Physical [Electrical and Optical parameters] Layer as well as the Application Layer, Network Layer, and Medium Access Control.
The MOST bus provides an optical solution for automotive media [entertainment] networks [Video, CD..].
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J1850 bus Description
The SAE J1850 bus is used for diagnostics and data sharing applications in On and Off road vehicles. The J1850 interface takes two forms; A 41.6Kbps Pulse Width Modulated (PWM) two wire differential approach, or a 10.4Kbps Variable Pulse Width (VPW) single wire approach. The single wire approach may have a bus length up to 35 meters (with 32 nodes). The J1850 interface was developed in 1994, J1850 may be phased out for new designs. The J1850 is a class B protocol. The J1850 protocol uses CSMA/CR arbitration. The frame consists of a Start Of Frame [SOF], which is high for 200uS. The Header byte follows the SOF and is one byte long.
The data follows the header byte. The one byte CRC [Cyclical Redundancy Check] follows the data field.
After the CRC an End Of Data [EOD] symbol is sent. The EOD is sent as a 200uS low pulse.
{Back to Automotive Bus Index}
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MI Bus Description
MI Bus (MI Bus [Motorola Interconnect] is a serial [Single wire] communications protocol with one Master and many Slaves.
The MI bus may applied to drive Mirrors, Seats, Window lifts or Head light levellers. The Master sends address and data [the Push Field] to all slaves on the bus.
The slave with the same address responds with the information requested [the Pull Field].
The Push field contains a Start bit [low for 3 bit times], a synchronization bit [bi-phase encoded 0], a data field [5 bits bi-phase encoded], and an address field [3 bits bi-phase encoded].
The Pull field contains a synchronization bit [bi-phase encoded 1], the data field [3 bits encoded NRZ], and a End of frame field [~ 3 cycles of a 20KHz square wave].
The single wire line operates between Logic 0 [0.3v maximum], and Logic 1 [+5 volts].)
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DSI Bus Description
DSI Bus [Distributed Systems Interface] developed by Motorola as a dedicated safety bus.
DSI is a two-wire serial bus linking safety-related sensors and components in vehicles.
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BST Bus Description
BST Bus [Bosch-Siemens-Temic] is another vehicle safety bus, used with air-bags (for example).
The BST bus is a 2-wire bus using Manchester encoding and either Parity or CRC for error correction and detection. The BST bus runs up to a maximum of 250Kbps.
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MML Bus Description
MML Bus [Mobile Multimedia Link] is multimedia bus.
The MML Bus uses plastic optical fiber technology in a star architecture via a Master/Slave communication approach.
MML Bus has an operation speed of 100Mbit/sec with a maximum cable length of 10 meters [that can't be right]. Encoding for MML is NRZ.
The MML bus is fault tolerant and handles plug and play.
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byteflight (SI-Bus) Description
byteflight is used for safety-critical applications in motor vehicles [air-bags]. Byteflight is a TDMA [Time Division Multiple Access] protocol that runs at 10Mbps over [2-WIRE or 3-WIRE] Plastic optical fibers [POF] in a bus, Star or Cluster configuration which provides an information update rate of 250uS. Byteflight is based on a message-oriented transmission process, with Master/Slave media access [all messages are made available to all bus subscribers at the same time]. The frame consists of a 6-bit Message Start sequence, an 8-bit message identifier [ID], one length byte [LEN], up to 12 data bytes can be transmitted in the following data field [D0 to D11].
After the data field a 2-byte [16-bit] CRC-sequence is sent [CRCH/CRCL].
{Automotive Bus Index}
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FlexRay Description
FlexRay is a high-speed serial [Synchronous and Asynchronous] communication system for in-vehicle networks [Control Systems] using Point-to-Point [Star topology] links, at 10Mbps [Fault-Tolerant] over Un-shielded Twisted Pair [UTP] or Shielded Twisted Pair [STP] cable.
The FlexRay bus defines the Physical layer [Electrical and Optical] and Protocol.
FlexRay is an extended protocol version of byteflight. Applications for FlexRay include; steer-by-wire and brake-by-wire.
{Automotive Bus Index}
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domestic digital data bus (D2B) Description
Domestic Digital Bus [D2B] is an optical data bus system connecting audio, video, computer peripheral and telephone components in a single ring structure within the vehicle.
Mercedes-Benz uses a combination ring and Star optical [650nm] topology at a speed of 5.6MBps [20MBps maximum].
The D2B interface has a maximum fiber distance of 10 meters [1 coupler] or 7 meters [2 couplers].
{Automotive Bus Index}
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SMARTwireX Description
SMARTwireX defines an electrical physical layer (PHY) supporting D2B networks running up to 25Mbps.
SMARTwireX runs over standard low-cost UTP cabling, with full automotive EMC compatibility.
SMARTwireX is an electrical physical layer solution for automotive networks.
Initially designed for D2B electrical networks, but potentially capable of supporting other networks as well.
SMARTwireX uses a Master/Slave approach connected via twisted pair, encoded as PWM. SMARTwireX has a maximum bus length of 150m [meters].
{Automotive Bus Index}
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IDB-1394 Bus Description
The IDB-1394 Bus is the Automotive version of the IEEE 1394 {Firewire}.
"IDB-C was the first of a family of in-vehicle serial communication protocol networks. IDB-C is defined in the SAE J2366 - ITS Data Bus series of specifications.
IDB-C is based on CAN 2.0B (Controller Area Network) silicon and physical layer, specifically on SAE J2284 - High Speed CAN."
There are four layers of the IDB protocol stack; J2366-1, Physical Layer, J2366-2, Link Layer, J2366-4, Thin Transport Layer, J2366-7, Application Message Layer.
The IDB is primarily used as a consumer device bus operating over an unshielded Twisted Pair [UTP] multidrop cable.
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IEBus Description
Inter Equipment Bus [IEBus] is used as an In-vehicle bus support using half duplex asynchronous [Multi-Master] communication with CSMA/CD for access control.
Two differential lines are used; Data+ / Data-. Two modes are defined: Mode 0 uses 16 bytes/frame and runs at 3.9kbps [6MHz Osc.] or 4.1kbps [6.29MHz Osc.].
Mode 1 uses 32 bytes/frame and runs at 17kbps [6MHz Osc.] or 18kbps [6.29MHz Osc.]. The IEbus allows 50 units on the bus over a maximum length of 50 meters.
The cable capacitance is rated to have 8000pF max [6MHz] or 7100pF max [6.29MHz]. The bus is terminated to 120 ohms. Each device on the bus has a 12 bit address.
The IEBus was developed by NEC Electronics. For a detailed description, and circuit Interface implementation; see the IEbus Interface page
{Automotive Interface Bus Index}
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LIN Bus Description
Local Interconnect Network [LIN] is used as an in-vehicle communication and networking serial bus between intelligent sensors and actuators.
The LIN specification covers the transmission protocol [Physical Layer and the Data Link Layer of LIN], and the transmission medium.
The LIN Bus is a class A protocol operating at a maximum bus speed of 19200 baud over a maximum cable length of 40 meters.
The specification may be obtained from LIN Consortium.
For a detailed description, Engineering Data, and circuit Interface implementation; see the LIN Bus page.
{Automotive Interface Bus Index}
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CAN Bus Description
CANbus Transceiver CAN Bus. A vehicle may have one or more CANbus implementations. An application for a low speed CANbus may include operate window and seat controls. A high speed CANbus may be employed for engine management or brake control, in addition to other applications.
The Controller Area Network (CAN) specification defines the Data Link Layer, ISO 11898 defines the Physical Layer. The CAN interface is an asynchronous transmission scheme controlled by start and stop bits at the beginning and end of each character. This interface is used, employing serial binary interchange. A class B, and Class C bus. Information is passed from transmitters to receivers in a data frame. The data frame is composed of an Arbitration field, Control field, Data field, CRC field, ACK field. The frame begins with a 'Start of frame', and ends with an 'End of frame' space. The data field may be from 0 to 8 bits.
The frame check sequence is derived from a Cyclic Redundancy Code (CRC);
the coefficients are generated modulo-2: X15 + X14 + X10 + X8 + X7 + X4 + X3 + 1
For additional information refer to: CAN Specification; Version 2.0, or ISO 11898/11519
Controller Area Network (CAN); ISO 11898/11519.
For a detailed description, Engineering Data, circuit Interface implementation and specifications; see the CANbus page.
The CAN bus page also lists additional protocols based on CAN bus.
{Automotive Interface Buses Index}
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Intellibus Description
Intellibus is a multi-drop communications bus developed by Boeing initially for military avionics applications, but also has an application in the automotive field. Similar to CAN in concept with similar limitations and inefficiencies. Intellibus operates at bus speeds of 12.5Mbps. Intellibus is used with electronic engine control, transmission, and other vehicle systems as another Drive-by-Wire protocol.
Intellibus uses a Master/Slave approach with Manchester Bi-Phase bit encoding over a twisted pair wire. The maximum bus length is 30 meters, at 12.5Mbps to a maximum of 64 nodes.
Intellibus provides both parity and CRC error detection. A class B, and Class C bus.
{Automotive Buses Index}
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OBDII Bus Description
OBDII Cable OBD2 [On-Board Diagnostics II] defines a communications protocol and a standard connector to acquire data from passenger cars. It was required by U.S. EPA on all gasoline powered cars and light duty trucks manufactured for the U.S. after 1996 to help monitor/inspect vehicle emissions.
OBDII will light a lamp called a MIL (malfunction indicator lamp), also known as the "check engine" light on the dash.
The OBD-II standard allows for multiple electrical interfaces, which complicates the hardware used to interface with the vehicle. OBDII data as defined by the SAE J1979 standard
SAE J1708 Bus Description
Serial Data Communications Between Microcomputer Systems in Heavy-Duty Vehicle Applications. J1708 defines the physical layer only. J1708 uses the RS485 bus as the electrical layer.
The cable is a 2-wire 18 AWG wire with a maximum distance of 40 meters. Class A operating to 9600bps. A message starts with a Message Identification Character [MID], followed by Data characters and then a checksum.
The total message length is 21 or less characters. Each character is 10 bits, each character begins with a Start bit [logic low].
{Automotive Buses Index}
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Vehicle Area Network
VAN An automotive bus developed by Peugeot and Renault [early 1990's].
The VAN bus is a differential bus with Enhanced Manchester Data Encoding.
The Two-wire data bus consists of 'Data' and 'DataB'.
The VAN network may have one or more Masters and some number of Slaves.
The VAN Networking Topology may be interconnected in a number of different architectures.
VAN may be either a BUS, Ring, Tree or Star style using broadcast or point-to-point communications.
ISO standard 11519-3 [VAN Protocol]. Transmission speed 160kHz [estimate].
IC Interface MTC-30521, Alcatel. VAN Data Link Controller TSS461F, Atmel.
The resistors [R2] shown in the graphic are for impedance balance of the VAN Bus.
Resistors R1 and Capacitors C1 form a low pass filter [Ri / RiB] which then feeds the comparators.
The normal circuit output is from Ro. However is either Data or DataB fail, the output can still be reconstituted.
The Ro can be used with one of the two supplementary comparators [either R1 or R2] to allow communication, even though one line has failed.