TTP/C组籍算法存在的问题

TTP/C通信协议已经应用于一些航空航天与地铁系统中,例如,空客A380的舱压控制系统、波音787梦想客机的辅助电源系统、环境控制系统等。以往我们仅看到对这种协议种种好处的分析,这是不全面的,它的组籍算法是高可信赖性应用的基础,但是其故障假设不符合很多现场使用环境,故障假设失效的概率大于功能安全容许的指标,协议的CRC检验将组籍向量的差包含在内,弱化了检错能力,所以需要用户特别重视。本文就这两点加以说明。

Problems in TTP/C Membership Algorithm

TTP/C communication protocol is used in some aerospace and subway systems such as the cabin pressure control system in A380,the auxiliary power supply system in Boeing 787 and the environment control system.The advantages of TTP/C protocol have been widely described,but it has some problems in fact.The membership algorithm makes that the protocol meets the needs of high reli-able applications,but its fault hypothesis is not compatible with the actual application environment.Its fail probability is higher than the allowable value of function safety and CRC check includes the difference value of membership vectors,so that the ability of error detection is weakened.Users should pay attention to these problems,so this paper analyzes these problems in detail.