Talks and Poster Presentations (with Proceedings-Entry):
W. Elmenreich, M. Delvai:
"Time-Triggered Communication with UARTs";
Talk: IEEE International Workshop on Factory Communication Systems,
- 2002-08-30; in: "Proceedings of the 4th IEEE International Workshop on Factory Communication Systems",
The simple UART encoding is used in two novel fieldbus protocols for real-time systems, the Local Interconnect Network (LIN) and the Time-Triggered Protocol for SAE class A applications (TTP/A). These protocols use a time-triggered communication schedule to achieve a predictable timing behavior. The employment of standard components like a standard Universal Asynchronous Receiver and Transmitter (UART) reduces costs, but the issues of clock drift, send jitter, and the adjustability of the send frequency have to be considered.
It is the objective of this paper to examine common timing problems with standard UARTs and presents a calculation for upper bounds for the timeliness of UART driven communications.
Furthermore we describe methods for circumvention of these timing problems. One method relies on the design of the communication protocol, the other way proposes a special UART design.
Case studies for these two methods are given by the TTP/A protocol and a compact VHDL model of a UART that behaves better for time-triggered systems than standard UARTs.
Electronic version of the publication:
Created from the Publication Database of the Vienna University of Technology.