Time-Triggered Protocol
Encyclopedia
TTP is an open and modular control system
platform technology that supports the design of upgradeable, reusable and easy-to-integrate systems. As a time-triggered fieldbus
, it can significantly impact the design of modern electronics and control system architectures for next-generation vehicles and industrial applications.
TTP was originally designed at the Vienna University of Technology
in the early 80s. From 1998 onwards TTTech Computertechnik AG
has taken over the further development of TTP, providing software and hardware solutions for this data communication protocol. Today TTP communication controller chips and IP are available from multiple sources including austriamicrosystems
(SWX: AMS), ON Semiconductor
(NASDAQ: ONNN) and ALTERA
(NasdaqGM: ALTR).
As a fault-tolerant time-triggered protocol, TTP provides autonomous fault-tolerant message transport at known times and with minimal jitter by employing a TDMA (Time-Division Multiple Access
) strategy on replicated communication channels. TTP offers fault-tolerant clock synchronization
that establishes the global time base without relying on a central time server.
TTP provides a membership service to inform every correct node about the consistency of data transmission. This mechanism can be viewed as a distributed acknowledgment service that informs the application promptly if an error in the communication system has occurred. If state consistency is lost, the application is notified immediately.
Additionally, TTP includes the service of clique avoidance to detect faults outside the fault hypothesis, which cannot be tolerated at the protocol level.
). The schedule is stored in the MEDL (Message Descriptor List) within the communication controller. The figure below gives a better understanding of those technical terms.
.
LockTrac 6131 ELEKTRA is an electronic interlocking system that provides the highest levels of safety and availability. The system is approved according to CENELEC standards with safety integrity level 4 (SIL4
) and offers basic interlocking functions, local and remote control, automatic train operation, integrated block functionality and an integrated diagnosis system. LockTrac 6131 has two software channels with diverse software, to ensure the high safety requirements. Before getting transmitted externally, the data are checked in the safety channel. A diagnosis device saves all relevant information to allow efficient maintenance in case of failure.
systems.
The Modular Aerospace Control (MAC)-based FADEC for The Aermacchi M346 is scalable, adaptable and fault-tolerant. The key technology enabler in this new FADEC is the use of TTP for inter-module communication. TTP removes the complex interdependencies among modules, simplifying initial application development as well in-service changes and upgrades. It allows all modules in a system to see all data all of the time, thus ensuring seamless fault accommodation without complex channel change logic.
TTP-based Modular Aerospace Control (MAC), which is a part of the F110 full authority digital engine control (FADEC) system of General Electric
, is integrated on the Lockheed Martin F-16 fighter aircraft. TTP, which is used as a backplane bus, supports high levels of engine safety, operational availability and reduced life cycle cost. A significant advantage is that all information on the bus is available to both FADEC channels simultaneously.
TTTech developed the internal communication system for the cabin pressure control system, working together with Nord-Micro, a subsidiary of Hamilton Sundstrand Corporation
.
In cooperation with Hamilton Sundstrand Corporation
, TTTech
developed a TTP-based data communication platform for the electric and environmental control system of the Boeing 787
Dreamliner. The TTP-designed communication platform prevents an overload in the bus system, even if several important events occur simultaneously. Additionally, TTP-based systems weigh less than conventional systems due to a lower connecter count and less wiring. Furthermore, the whole system is more flexible and has a greater modularity than conventional communication systems.
were implemented with "drive-by-wire" technology, in which on-board computers controlled steering, braking and other movements. Three TTP-based TTC 200 units controlled the parking brake and throttle and transmission functions, and one TTP-By-Wire Box controlled the service brake of the H1 Hummer H1ghlander. Drive-by-wire modifications controlled the acceleration, braking and shifting of the Sandstorm.
Control system
A control system is a device, or set of devices to manage, command, direct or regulate the behavior of other devices or system.There are two common classes of control systems, with many variations and combinations: logic or sequential controls, and feedback or linear controls...
platform technology that supports the design of upgradeable, reusable and easy-to-integrate systems. As a time-triggered fieldbus
Fieldbus
Fieldbus is the name of a family of industrial computer network protocols used for real-time distributed control, now standardized as IEC 61158....
, it can significantly impact the design of modern electronics and control system architectures for next-generation vehicles and industrial applications.
TTP was originally designed at the Vienna University of Technology
Vienna University of Technology
Vienna University of Technology is one of the major universities in Vienna, the capital of Austria. Founded in 1815 as the "Imperial-Royal Polytechnic Institute" , it currently has about 26,200 students , 8 faculties and about 4,000 staff members...
in the early 80s. From 1998 onwards TTTech Computertechnik AG
TTTech
TTTech Computertechnik AG is an Austrian company that provides solutions in the field of time-triggered computer systems. TTTech’s technologies and products, based on TTP, TTEthernet and FlexRay, improve the reliability of networked computer systems in the transportation and automation industries...
has taken over the further development of TTP, providing software and hardware solutions for this data communication protocol. Today TTP communication controller chips and IP are available from multiple sources including austriamicrosystems
Austria Microsystems
austriamicrosystems AG, frequently still known as AMS , is a multinational semiconductor manufacturer. The headquarters are located in Unterpremstätten...
(SWX: AMS), ON Semiconductor
ON Semiconductor
ON Semiconductor , is a semiconductors supplier company. Products include power and signal management, logic, discrete and custom devices for automotive, communications, computing, consumer, industrial, LED lighting, medical, military/aerospace and power applications...
(NASDAQ: ONNN) and ALTERA
Altera
Altera Corporation is a Silicon Valley manufacturer of PLDs . The company offered its first programmable logic device in 1984. PLDs can be reprogrammed during the design cycle as well as in the field to perform multiple functions, and they support a fairly fast design process...
(NasdaqGM: ALTR).
Definition
TTP is a dual-channel 25 Mbit/s time-triggered field bus. It can operate using one or both channels with maximum data rate of 2x 25 Mbit/s. With replicated data on both channels, redundant communication is supported.As a fault-tolerant time-triggered protocol, TTP provides autonomous fault-tolerant message transport at known times and with minimal jitter by employing a TDMA (Time-Division Multiple Access
Time division multiple access
Time division multiple access is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This...
) strategy on replicated communication channels. TTP offers fault-tolerant clock synchronization
Clock synchronization
Clock synchronization is a problem from computer science and engineering which deals with the idea that internal clocks of several computers may differ. Even when initially set accurately, real clocks will differ after some amount of time due to clock drift, caused by clocks counting time at...
that establishes the global time base without relying on a central time server.
TTP provides a membership service to inform every correct node about the consistency of data transmission. This mechanism can be viewed as a distributed acknowledgment service that informs the application promptly if an error in the communication system has occurred. If state consistency is lost, the application is notified immediately.
Additionally, TTP includes the service of clique avoidance to detect faults outside the fault hypothesis, which cannot be tolerated at the protocol level.
Frame, Message, Slot, TDMA Round and Cluster Cycle
Data communication in TTP is organized in TDMA rounds. A TDMA round is divided into slots. Each node in the communication system has one slot – its sending slot – and must send frames in every round. The frame size allocated to a node can vary from 2 to 240 bytes in length, each frame usually carrying several messages. The cluster cycle is a recurring sequence of TDMA rounds; in different rounds different messages can be transmitted in the frames, but in each cluster cycle the complete set of state messages is repeated. The data is protected by a 24-bit CRC (Cyclic Redundancy CheckCyclic redundancy check
A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...
). The schedule is stored in the MEDL (Message Descriptor List) within the communication controller. The figure below gives a better understanding of those technical terms.
Clock synchronization
The clock synchronization is necessary to provide all nodes with an equivalent time concept. Each node measures the difference between the a priori known expected and the observed arrival time of a correct message to learn about the difference between the sender’s clock and the receiver’s clock. A fault-tolerant average algorithm needs this information to periodically calculate a correction term for the local clock so that the clock is kept in synchrony with all other clocks of the cluster.Membership and Acknowledgment
A major philosophy in the design of TTP is that the protocol should transmit data consistently to all correct nodes of the distributed system and that, in case of a failure, the communication system should decide on its own which node is faulty. These properties are achieved by the membership protocol and an acknowledgment mechanism.Thales Rail Signalling Solutions
The electronic interlocking system “LockTrac 6131 ELEKTRA” was designed within a cooperation of Thales Rail Signalling Solutions division and TTTechTTTech
TTTech Computertechnik AG is an Austrian company that provides solutions in the field of time-triggered computer systems. TTTech’s technologies and products, based on TTP, TTEthernet and FlexRay, improve the reliability of networked computer systems in the transportation and automation industries...
.
LockTrac 6131 ELEKTRA is an electronic interlocking system that provides the highest levels of safety and availability. The system is approved according to CENELEC standards with safety integrity level 4 (SIL4
Safety Integrity Level
Safety Integrity Level is defined as a relative level of risk-reduction provided by a safety function, or to specify a target level of risk reduction. In simple terms, SIL is a measurement of performance required for a Safety Instrumented Function ....
) and offers basic interlocking functions, local and remote control, automatic train operation, integrated block functionality and an integrated diagnosis system. LockTrac 6131 has two software channels with diverse software, to ensure the high safety requirements. Before getting transmitted externally, the data are checked in the safety channel. A diagnosis device saves all relevant information to allow efficient maintenance in case of failure.
FADEC
The system has been used for FADEC (Full Authority Digital Engine Control)FADEC
Full Authority Digital Engine Control is a system consisting of a digital computer, called an electronic engine controller or engine control unit , and its related accessories that control all aspects of aircraft engine performance...
systems.
The Modular Aerospace Control (MAC)-based FADEC for The Aermacchi M346 is scalable, adaptable and fault-tolerant. The key technology enabler in this new FADEC is the use of TTP for inter-module communication. TTP removes the complex interdependencies among modules, simplifying initial application development as well in-service changes and upgrades. It allows all modules in a system to see all data all of the time, thus ensuring seamless fault accommodation without complex channel change logic.
TTP-based Modular Aerospace Control (MAC), which is a part of the F110 full authority digital engine control (FADEC) system of General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
, is integrated on the Lockheed Martin F-16 fighter aircraft. TTP, which is used as a backplane bus, supports high levels of engine safety, operational availability and reduced life cycle cost. A significant advantage is that all information on the bus is available to both FADEC channels simultaneously.
Environmental Systems
For the Airbus A380Airbus A380
The Airbus A380 is a double-deck, wide-body, four-engine jet airliner manufactured by the European corporation Airbus, a subsidiary of EADS. It is the largest passenger airliner in the world. Due to its size, many airports had to modify and improve facilities to accommodate it...
TTTech developed the internal communication system for the cabin pressure control system, working together with Nord-Micro, a subsidiary of Hamilton Sundstrand Corporation
Hamilton Sundstrand
Hamilton Sundstrand, is a global corporation that manufactures and supports aerospace and industrial products for worldwide markets. It was formed from the merger of Hamilton Standard and Sundstrand Corporation in 1999. A subsidiary of United Technologies Corporation, HS is headquartered in Windsor...
.
In cooperation with Hamilton Sundstrand Corporation
Hamilton Sundstrand
Hamilton Sundstrand, is a global corporation that manufactures and supports aerospace and industrial products for worldwide markets. It was formed from the merger of Hamilton Standard and Sundstrand Corporation in 1999. A subsidiary of United Technologies Corporation, HS is headquartered in Windsor...
, TTTech
TTTech
TTTech Computertechnik AG is an Austrian company that provides solutions in the field of time-triggered computer systems. TTTech’s technologies and products, based on TTP, TTEthernet and FlexRay, improve the reliability of networked computer systems in the transportation and automation industries...
developed a TTP-based data communication platform for the electric and environmental control system of the Boeing 787
Boeing 787
The Boeing 787 Dreamliner is a long-range, mid-size wide-body, twin-engine jet airliner developed by Boeing Commercial Airplanes. It seats 210 to 290 passengers, depending on the variant. Boeing states that it is the company's most fuel-efficient airliner and the world's first major airliner to use...
Dreamliner. The TTP-designed communication platform prevents an overload in the bus system, even if several important events occur simultaneously. Additionally, TTP-based systems weigh less than conventional systems due to a lower connecter count and less wiring. Furthermore, the whole system is more flexible and has a greater modularity than conventional communication systems.
Autonomous Vehicles
The two Red Team robotic vehicles competing in the 2005 DARPA Grand ChallengeDARPA Grand Challenge (2005)
The second driverless car competition of the DARPA Grand Challenge was a off-road course that began at 6:40am on October 8, 2005. All but one of the 23 finalists in the 2005 race surpassed the distance completed by the best vehicle in the 2004 race...
were implemented with "drive-by-wire" technology, in which on-board computers controlled steering, braking and other movements. Three TTP-based TTC 200 units controlled the parking brake and throttle and transmission functions, and one TTP-By-Wire Box controlled the service brake of the H1 Hummer H1ghlander. Drive-by-wire modifications controlled the acceleration, braking and shifting of the Sandstorm.
See also
- CANController Area NetworkController–area network is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer....
- FlexRayFlexRayFlexRay is an automotive network communications protocol developed by the . It is designed to be faster and more reliable than CAN and TTP, but is also more expensive...
- AFDX
- TTTechTTTechTTTech Computertechnik AG is an Austrian company that provides solutions in the field of time-triggered computer systems. TTTech’s technologies and products, based on TTP, TTEthernet and FlexRay, improve the reliability of networked computer systems in the transportation and automation industries...
- TTP/ATTP/ATTP/A is a time-triggered real-time fieldbus protocol used for the interconnection of low-cost smart transducer nodes. In contrast to Time-Triggered Protocol , which is a high-speed, fault-tolerant communication network intended for safety critical applications , TTP/A provides a low-speed ,...
- TTEthernetTTEthernetTTEthernet is a computer network technology marketed by TTTech Computertechnik AG for use in airplanes and other real-time applications.-Description:...