Terminology » TTP Protocol: Key Benefits, Features & Limitations

TTP Protocol: Key Benefits, Features & Limitations

automotive ttp protocol

Introduction : TTP (Time Triggered Protocol) enables deterministic and fault tolerant communication for safety critical vehicle systems.

What is TTP Protocol?

In the high stakes world of safety critical automotive systems, where a millisecond can make all the difference, the Time Triggered Protocol (TTP) stands out as a communication standard built on a foundation of predictability and reliability. Unlike event triggered protocols like CAN, which react to events as they occur, TTP orchestrates communication based on a pre-defined, globally synchronized schedule.

TTP Frame Formats

TTP enables time triggered communication through strict Time Division Multiple Access (TDMA) scheme.

Advantages of TTP

Following are some of the benefits of TTP.

  1. Determinism and predictability : It guarantees when messages will be sent and received.
  2. TTP was designed with fault tolerance as primary goal. It supports replicated channels and nodes to handle failures. Protocol includes mechanism known as “bus guardian” which can prevent a faulty node from disrupting entire network.
  3. TTP systems are temporally composable. This means behavior of individual subsystems can be analyzed and verified independently.
  4. It simplifies error detection as message arrival times are known in advance.
  5. By eliminating the need for bus arbitration, TTP can achieve higher effective data rates compared to older protocols like CAN. The protocol’s message overhead is also minimal.
  6. TTP provides a membership service that keeps all correct nodes informed about the status and consistency of data transmission from other nodes.

Disadvantages of TTP

Following are some of the limitations of TTP.

  1. The static nature of the TDMA schedule makes TTP less flexible than event-triggered protocols.
  2. While efficient for periodic data, the pre-allocated slots can be wasteful if a node only needs to transmit data sporadically.
  3. The upfront design and scheduling of a time triggered system can be complex.
  4. The specialized hardware controllers required for TTP could be more expensive than those for more widespread protocols like CAN.

Conclusion: In summary, it offers benefits like guaranteed latency, system scheduling and redundancy but also limitations such as higher cost, design rigidity and complexity in network configuration.