The Time Triggered Protocol (TTP) was developed by professor Herman Kopetz and is now owned and marketed by TTTech Computertechnik GmbH (Vienna), a startup created to commercialize the technology. But as pressure grows for automakers to implement brake-by-wire and steer-by-wire systems, a consortium including DaimlerChrysler AG (Berlin) and BMW AG (Munich) has begun looking for an alternative.

The problem lies in the licensing terms being attached to TTTech's patents, sources said, and with the Austrian company's alleged reluctance to incorporate changes carmakers and their chip suppliers say they need if they are to use TTP commercially. For its part, TTTech said it has always been willing to make changes to its protocol, to license its patents on reasonable terms and to open the TTPForum, now an interest group, into a standardization body.

Nevertheless, DaimlerChrysler now has joined BMW in an effort to develop a new safety-critical bus to use for implementing by-wire features in future automobiles. Martin Peller, an engineer at BMW, said that DaimlerChrysler and BMW, together with a number of semiconductor companies, are working on a bus that would sidestep TTP and associated patents, and will eventually offer it to the automotive industry.

Another direction

"It's true DaimlerChrysler and BMW are going in another direction to that which TTTech is suggesting," Peller said, promising that the two "will come out with common information at around the time of the next VDI meeting in September or October." VDI is the German engineering society.

Peller himself has worked on a passive safety-critical bus for BMW called Byteflight, with help from chip makers Infineon Technologies, Motorola and Elmos.

Because Byteflight is less rigorously specified than TTP/C, the version of TTP designed for so-called C-class safety issues, it is suitable for only passive safety systems such as airbag deployment, and not for active ones like brake- and steer-by-wire systems. The new initiative is intended to provide a higher level of robustness for such applications. Redundancy support, which is not present in Byteflight, is one of the issues expected to come up for debate within the safety-critical bus industry forum BMW is putting together.

"The name of the new standard won't be Byteflight-2, but the heart of Byteflight will be in there," said Peller. "TTTech does hold some patents in the area of safety-critical communications protocols, but our legal people have looked into this and advise us we do not need to license them."

Aside from licensing issues, some automotive engineers say that TTP/C needs to be tweaked for commercial use, but that TTTech has stonewalled such requests.

Though TTP is valued for its determinism and fault-tolerance, "TTP/C as it is defined and implemented today does not fulfill the requirements for automotive safety applications," said Wilhard von Wendorff, senior system engineer for automotive-system safety and security at Infineon Technologies AG (Munich). "It is not composable enough and has problems with the so-called membership function. Therefore, three major automotive companies approached Professor Kopetz, the owner of the relevant patents, to modify the TTP/C. Professor Kopetz does not see the necessity to do so."

At the same time, von Wendorff said, the licensing terms do not allow semiconductor vendors to do modifications on their own. If they do, they "lose the right to the patents," he said.

Georg Kopetz, managing director of TTTech and the son of Herman Kopetz, maintains that the company is willing to "accept any changes to make the protocol better." However, "TTP is very carefully thought out and safe," he said. "All we have said is that if people license the patents and then amend the protocol they shouldn't call the new protocol TTP."

Kopetz vowed that TTTech "would license patents for TTP/C on a reasonable basis," and said the company intends to "open the technology up to international standardization." That could be done, he said, by sharing the ownership of the technology through the TTPForum, following the lead of other ad hoc groups such as the WAP Forum for wireless communications.

Hit the road

But von Wendorff remains unimpressed. "For one year now we have been discussing one sentence in the licensing terms and conditions. We haven't got time. We have to get it on the road."

With regard to opening up the TTPForum, von Wendorff said, "We discussed it already in 1998. It never happened."

The Infineon engineer said he believes TTP/C is the best starting point to develop a new deterministic and composable bus system for automobiles, but that various legal and commercial issues make its use seem less and less likely as time passes.

Motorola Inc., the leading supplier of silicon to the automotive industry, is a member of the TTPForum, worked with BMW on Byteflight and is thought to be a member of the new consortium forming around DaimlerChrysler and BMW.

Jim Trent, chassis systems operations manager at the advanced-vehicle systems division of Motorola's Semiconductor Products Sector, declined to confirm such reports, but said any disagreement over technology and royalties could affect the level of semiconductor makers' commitment to TTP.

"We're not backing this technology TTP just for the purpose of putting another protocol out there," said Trent. "Motorola is not going to invest in it unless we have an OEM lined up to help drive it through as an industry standard. Nor do we want to see competing protocols out there. We want to find a way to make this into one de facto standard."

That stance, Trent said, is a necessity at a time when automakers are increasingly pushing their chip suppliers to bear the brunt of the investment in new electronics technology, with no guarantee of success. He pointed to the adoption of controller-area network (CAN) technology by the automotive market, saying that OEM support brought it to the forefront at the expense of equally capable technologies, such as J-1850.

"There's no clear winner emerging here either," Trent said. "This looks very similar to the CAN situation. Our concern is that we will end up investing in something that will never be an industry standard. And then we never get a return on our investment."

The TTP has potential use in other safety-critical applications, such as railway signaling and aerospace, but it is with automotive suppliers that most research and project work has been done.

— Additional reporting by Charles J. Murray.