Loosely Time-Triggered Architectures based on Communication-by-Sampling
Résumé
We address the problem of mapping a set of processes which communicate synchronously on a distributed platform. The Time Triggered Architecture (TTA) proposed by Kopetz for the communication mechanism of a distributed platform offers a direct mapping that would preserve the semantics of the specification. However, its exact implementation may, at times, be problematic as it requires the distributed platform to have the clocks of its components perfectly synchronized. We propose as implementation architecture a relaxation of TTA called Loosely Time-Triggered Architecture (LTTA), in which computing units perform writes into and reads from the communication medium independently, triggered by local, quasi-periodic but non synchronized, clocks. LTTA offers some of the advantages of TTA with lower hardware cost and greater flexibility. So far LTTA was studied for single directional two-users communications over an LTT bus. General topology was not studied. In this paper we propose a design flow that ensures semantics preservation for an LTT communication network with arbitrary topology. Key elements are two new protocols for clock regeneration and predictive traffic shaping. Our approach relies on a mathematical Model of Communication (MoC) that we describe in detail.
Domaines
Autre [cs.OH]
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