Non pre-emptive scheduling of messages on SMTV token-passing networks

Fieldbus communication networks aim to interconnect sensors, actuators and controllers within distributed computer-controlled systems. Therefore, they constitute the foundation upon which real-time applications are to be implemented. A specific class of fieldbus communication networks is based on a simplified version of tokenpassing protocols, where each station may transfer, at most, one Single Message per Token Visit (SMTV). In this paper, we establish an analogy between non pre-emptive task scheduling in single processors and scheduling of messages on SMTV token-passing networks. Moreover, we clearly show that concepts such as blocking and interference in non pre-emptive task scheduling have their counterparts in the scheduling of messages on SMTV token-passing networks. Based on this task/message scheduling analogy, we provide prerun-time schedulability conditions for supporting real-time messages with SMTV token-passing networks. We provide both utilisation-based and response time tests to perform the pre-run-time schedulability analysis of realtime messages on SMTV token-passing networks, considering RM/DM and EDF priority assignment schemes. Neither this paper nor any version close to it has been or is being offered elsewhere for publication. All necessarily clearances have been obtained for the publication of this paper. If accepted, the paper will be made available in camera ready forms by March 15th, 2000, and it will be personally presented at RTS'00 by one of the authors. The presenting author(s) will pre-register for RTS'00 before the due dates of the camera-ready paper.