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.