Bus Systems Flashcards
AUTOSAR
Automotive Open System Architecture: Is an open and standardized automotive software architecture, jointly developed by automobile manufacturers, suppliers and tool developers.
TDMA
Time Division Multiple Access: Is used to implement time-triggered control where communication is organised into cycles. The cycles are structured uniformally and laid out according to a schedule, then structured into a number of time slots, each assigned to a bus node - this ensures deterministic communication
CAN
Controller Area Network:
CAN is a serical communication technology used especially for reliable data exchange between electronic control units (ECU’s) in the automobileCSMA/CA forms the basis of a CAN network,
On a CAN bus, bus access is exclusively priority-driven.
29 bits make up the CAN identifier in extended format.
LIN
Local Interconnect Network:
An OEM-independent communication standard, which allows time-triggered bus access for simple and cost-effective data exchange in the automobile. Many automotive OEMs today rely on LIN to transmit non-critical signals in the convenience area using a single-wire line without shielding as its typical transmission medium.
Maximum data transmission rate: 20 KBit/s
MOST
Media Oriented Systems Transport:
TSN
Time Sensitive Networking:
PWM
Pulsweitenmodulation: Ist eine Modulationsart, bei der eine technische Größe (z.B. elektrische Spannung) zwischen zwei Werten wechselt. Dabei wird bei konstanter Frequenz der Tastgrad eines Rechteckpulses moduliert, also die Breite der ihn bildenden Impulse.
ARA
Autosar Runtime Environment for Adaptive Applications
ARA::com
see ARA: Service-oriented communication. It is the communication part of Adaptive Autosar
CiA
CAN in Automation
PlS
Physical Layer Signalling
ISO 11898
CAN (Controller Area Network)
CRC
Cyclic Redundancy Check: This protects the useful data in a CAN data transmission by appending a checksum to the useful data, which is evaluated by the receiver by applying the CRC algorithm.
CSMA/CA Method
Carrier Sense Multiple Access/Collision Avoidance:
A demand based bus access system that reacts quickly to events and ensures that CAN nodes wishing to send do not access the CAN bus until it is available. It also ensures that the CAN node with the highest priority data frame prevails and is therefore especially well suited for demand-based data communication.
Bit Stuffing (CAN)
Bit Stuffing is the insertion of non information bits into data. A bit of opposite polarity is inserted after five consecutive bits of the same polarity and is used to ensure the sychronisation of all nodes
SCI
Serial Communication Interface: Serial data transmission in a LIN network is handled over the microcontrollers SCI due to the lack of a communication controller, which is performed by so-called SCI frames.
FlexRay
FlexRay was primarily developed to provide extremely reliable and safe data transmission in safety-critical automotive applications through time-triggered bus access. It was created with the knowledge that CAN will not be able to meet the growing requirements for data transmission in the automobible over the mid-term.
Data protection is provided by both physical and logical measures.
A Ring topology cannot be used as the basis for a FlexRay network.
FTDMA
Flexible Time Division Multiple Access:
To combine the two approaches to bus access used by FlexRay (for deterministic transfer properties, it offers time-controlled bus access / for applications whose transfers place less demanding requirements on transfer properties, it is desirable to make as effective use of the available transfer capactiy as possible.
With each cycle there is first a static tranmsision component in which bus access is controlled by TDMA. Then follows a dynamic transmission component in which bus access is controlled by the use of minislots. Minislots are small time windows in which a defined message can be tranferred. This access method is known as Flexible Time Division Multiple Access.
Topology
Topology:
Or network topology is understood as the internconnection of structure among the communication participants in serial communication systems. In networking electronic control units in vehicles, standard topologies generally used are: Star, Ring, and Bus topology. As the choice of certain topology has wide-ranging consequences for the performance of a serial communication system, this decision should not be made without considering the system’s duty conditions.
Star Topology
Star Topology:
Serial communication systems with a star topology are characterized by a special node (center point hub) to which all communication participants are connected in a star shape. Such star-shaped communication systems are ideal for implementing a master-slave architecture with a centralized control bus access method.
Because each communication node is connected point-to-point to the central node, failure of one communication node does not lead to failure of the communication system. In additoin, different transmission media may be used. The disadvantage of star-shaped communication systems lies in their limited availability: failure of the center node leads to failure of the entire communication system. In addition, wiring expense is relatively large.
Bus Topology
Bus Topology:
Very widely used in the motor vehicle are serial bus systems, i.e. serial communication systems based on a bus topology. CAN, LIN, and FlexRay are all based on the bus topology; all communication participants (bus nodes) are connected passively to a common transmission medium (bus). Because by definition all data reach all bus nodes in a serial bus system, a serial bus system is implicitly a diffusion network or broadcast system.
A significant advantage of serial bus systems is that they permit any desired logical interaction structures. Also advantageous are the low wiring expense and easy extendability. However, it’s bus length and number of bus nodes are limited, because signal regeneration is not typically performed in serial bus systems. Additionally, long electrical lines must be terminated by a so-called “characteristic impedance” to prevent signal reflections at the line ends. And finally, a break in the transmission medium leads to failure of the communication system.
Ring Topology
Ring Topology:
If it is necessary to combine spatially distant communication participants into one serial communication system, the ring topology is generally used. All communications nodes are internonnected poitn-to-point to form a ring, and they each act as an ampliflier here. Bus access is usually implemented by a symbol (Token) that circulates around the ring.
A key advantage of the ring topology is that different transmission media may be used for each individual sub-section of the ring. It is also suitable for implementing larger networks.
The disadvantage of this topology is that a failure of one communication node leads to failure of the entire communication system, unless special preventive measures are taken. Therefore, broad considerations are given to safety in ring networks.
Token Ring
Token Ring:
Delegated Token
Delegated Token:
Superposition Principle
Superposition Principle:
Proportionality Principle
Proportionality Principle:
Principle of Total Reflection
Principle of Total Reflection:
Maxwell Principle
Maxwell Principle:
CAN FD
CAN FD:
When CAN was originally developed there number of signals to be communicated were in the order of hundreds, now there are thousands. This led to the ever higher bus loads on CAN buses.
CAN’s lack of bandwidth is often circumvented by applying a higher number of CAN buses. But this involves using gateways to transfer data between these buses.
Instead, with CAN FD the transmission rate is increased during the arbitration phase and the acknowledgement field of a CAN frame, where only one transmitter is allowed. So with CAN FD you have two different transmission rates,: A slow one at the beginning and end of a CAN frame an da fast one in the middle.
