TTEthernet

Since the classic Ethernet is not suitable for real-time applications due to its stochastic access method and the frame length, various Ethernet variants have been developed to circumvent this limitation. In addition to EtherCat, EtherNet/ IP and Ethernet Powerline, TTEthernet should also be mentioned. Whether the letters TT stand for Time Triggered or for the Austrian TTTech Computertechnik AG, which developed TTEthernet, is not known.

The concept is an Ethernet-based network with real-time behavior that can be used in industry, production and also in safety-critical applications in aircraft and automotive technology. It combines the techniques of Time Triggered (TT), as realized in the TTP protocol and in the TTP/A and TTP/C bus, with those of open Ethernet.

TTEthernet controls media access in such a way that time-critical information has priority over less time-critical information. It also uses Bandwidth Allocation Gap( BAG) to determine the frame length. The time-critical messages use a deterministic access method with which the quality of service can be characterized and the timing can be determined exactly. For this purpose, in this real-time Ethernet the messages are transmitted by means of Time Triggered (TT) at precisely specified times. In addition to this TT communication class, there are two others: Rate Constrained Communication( RC) and Best Effort Communication( BE).

Rate Constrained Communication does not place such high demands on real-time behavior. It only ensures that messages arrive within a certain time period. The RC messages are not synchronized and no control information is required. In the best- effort principle, messages are delivered on a best-effort basis. No guarantee is given for their delivery.

TTEthernet is a scalable Ethernet platform for safety and time-critical applications for the transportation and automation industries. It is compatible with Ethernet and can work with existing Ethernet components.