A real-time upgrade for Ethernet based factory networking

Efficient transfer of information between all levels of a manufacturing organisation is becoming an increasingly essential element in maintaining industrial competitiveness. Since manufacturing is a distributed activity with varying levels of time-criticality at different levels in the hierarchy, the architecture of the computer communication networks must match these fundamental requirements. One appropriate solution is the General Motor´s Manufacturing Automation Protocol local area network-MAP. Another possibility, proposed in this paper, is to use Ethernet for higher level communications, where time is less critical, and to supplement this with a “real-time Ethernet” at the lower levels. This paper therefore describes a system designed to convert segments of a factory wide Ethernet network to support hard real-time operation. The system, called TEMPRA, uses a simple method to control the release of Ethernet packets in a collision free manner. High priority real-time operation is guaranteed to the user through a dual stack architecture, which has a separate deterministic stack for high reliability real-time messages-whilst background traffic is handled using CSMA/CD and TCP/IP protocols